This article was written a while ago and is aimed at the Diamond environment.  I'll be updating it shortly to include all recent expansions (up to Code of Bushido) and what is on the Lotus pdf

Spell Analysis for the current environment: (to be updated as I get to it)
(just my opinion, for whatever it's worth)
For those of you who are veterans: you probably know most of this already, feel free to comment, add, dispute, etc.  That's what this is here for.
For those of you who are new: read, enjoy, and experiment on your own.  This is supposed to be a guide, not a definitive answer.

Format:
What it does…
(Good) Where it might be good…
(Bad) Where it might be bad…
(Ugly) What snazzy combos are there…

Common abbreviations:
KA = Kyuden Agasha (Diamond Edition)
MGC = Morning Glory Castle (Diamond Edition)
CoR = City of Remembrance (Reign of Blood)
CoB = City of Blood (Web of Lies)

Kuro's Fire
Elemental Battle: Bow this Shugenja to make a number of consecutive ranged attacks up to the Shugenja's Chi. The ranged attacks' total strength cannot exceed the Shugenja's Force plus Chi. (Consecutive ranged attacks are targeted and resolved one at a time.)

Good: Wow, massive ranged death.  This can be great in just about any Phoenix deck.  On the defense, you can blast away many of the opponent's units before he even gets to react.  The multi ranged attacks help you split damage between followers and personalities.  Thus peeling off protective followers before smoking the people behind them.

Bad: Not really any bad.  It doesn't cost that much for what it does, even in a non-Kyuden Agasha stronghold.  If you are playing some sort of box party with all cheap shugenja that have low force and low chi (e.g. Agasha Seruma), it may not be worth your while.

Ugly: It's one of the main components to Voltron/Death Star.  If you are not familiar with that terminology, it is a unit that consists of Agasha Chieh, Kuro's fire, Isawa House Guard, The Celestial sword, and some Speed of the Plains for an unfathomable amount of ranged attacks at a ridiculously high rate of speed without time for retribution.  Although, in the current control heavy environment, one super unit is NOT a wise idea.  Is Voltron dead?  Maybe…

Touching the Elements
Air Open: Bow this Spell to turn one face-down card in a Province face-up.
Earth Open: Bow this Spell to give a Personality +1F.
Fire Battle: Bow this Spell for a Ranged 1 Attack.
Water Open: Bow this Spell to give a Personality +1C.

Good: Variety, adaptability, and multiple elemental traits.  You can use this ultra cheap spell in just about any deck.  Dueling? use the chi boost, Attacking? Use the force boost, Playing box party? Turn some provinces face up after events or regions.

Bad: Has very little use in an MGC honor rocket or a CoB blitz, but pretty useful in just about everything else.

Ugly: My favorite has to be "Strength in numbers".  I love playing classic Samurai/Shugenja military.  This is a keystone card to that.  Seeing that most of the Phoenix Shugenja have at least one elemental trait on them already, this puts you 2/3s of the way there.  Then, just bow a Tsukimi to blow up any offending unit.

Fire from Within
Elemental Battle: Bow this Shugenja for two consecutive Ranged Attacks with strengths equal to his Chi. (Consecutive ranged attacks are targeted and resolved one at a time.) Elemental Battle: Bow this Shugenja for a Ranged Attack with strength equal to twice his Chi.

Good: There is something to be said for the defensive power the Phoenix have when sitting back with massive ranged attacks at their disposal. These aren't little Ranged 3 Mantis attacks, these are often a abase strength of 4 or 5 that get doubled to 8 or 10.  If some fool is going to attack you, he'll think twice when facing a few of these.

Bad: In a CoR deck, you have better things to use a Dragon for than his 4 chi.

Ugly:  You might call it "poor man's Kuro's Fire".  You can use it to add to the ranged attack death of a defensive deck.  Imagine all three Kuro's and all 3 FfWs out at the same time, guh.

Blood Command
Will only attach to a Bloodspeaker. Maho Battle: Once per battle, without bowing, bow an opposing Personality with lower Chi.

Good:  Hey, it's free bow tech.  Who would fuss at that?, especially because most shugenja have high Chi.  You don't even have to bow, saving yourself for more spells.

Bad: Only for bloodspeakers (therefore really only good in CoB).  High cost outside of KA.  You have to be in a battle and are therefore vulnerable.

Ugly:  Slap a couple of these on your auto-bloodpseakers in a CoB deck and sail into battle.  You can use available chi lowering tech to ensure just about any of your opponent's units will suffer this fate.  It will then combo nicely with Blood-soaked Ground.

Cloak of Night
Limited: Bow this Shugenja and destroy Cloak of Night to attach a Spell, Follower, or Item from your hand to one of your Personalities, face-down and without cost. While face-down, that card is not in play and does not affect play. As an Open action any time later this game, you may turn the card face-up to bring it into play. If the card is not a legal attachment at that time, discard it; otherwise it enters play without cost.

Good: If you have an expensive attachment heavy deck, this is the way to go.  Do you desperately need your Celestial sword?  How about 4 gold for it. Want to spring a Bishamon's fury on your opponent?  4 gold and speed of the plains and there is nothing for him to do except weep.

Bad:  If you have the spell and nothing to attach, it's dead weight.  If your attachments aren't more than 4 gold, it's just a little trickery, you be better off with ciphered scroll (heh). 

Ugly: The Bishamon's Fury and Speed of the plains is about the nastiest combo I can think of off the top of my head.

Essence of Gaki Do
Ritual Battle: Bow this Shugenja and any number of additional Shugenja to create an equal number of 2F/2C Unaligned Spirit Personality cards under your control in the current battle. Remove them from play after the battle ends.

Good: This spell is a win condition all to itself.  Just sit at home, declare an attack, resolve an undefended province and start casting.  This works only with a Phoenix box party deck because you need many shugenja as fast as possible.  Win a few early battles by avoiding their armies (even Unicorn) and cut their resources down.  Keep in mind that if they spread their defense out across all their provinces, you can still pile up on one and kill their personality.

Bad: If you have no way to protect your provinces, bowing out your personalities for a turn with a 6 province strength is not a good idea.  You need Call to arms, Sezaru, lots of send home tech, and probably a Naga Storm Mirumoto Mountain.

Ugly: Don't forget that after you create these spirits in a battle, they are yours to do with as you wish.  Is your opponent defending with some big monster of a bezerker?  Have him say hello to your "overwhelmed".  Damn, you lost a 2/2 spirit, what a shame.  If you happen to have your Voltron (Chieh) out, you can send a Kuro's Fire postcard to the battle.

Bishamon's Fury
You may bring this card into play from your hand as a Battle action. If you do, you may gain an additional Battle action to use the following ability. Ritual Battle: Bow and destroy a number of Shugenja Personalities you control, including this one, equal to the number of targets: Target any number of opposing units. Destroy them.

Good: In-battle PK is always good because you do not win military with a few super units.  When your opponent bravely sends his swollen up Oni/Unicorn/Berzerkers over to say "hi", just set him up with a Bishimon's Fury.  It can take out any opposing unit, regardless of attachments.  Very nice.

Bad:  Unless you are KA, it's expensive.  Maybe prohibitively so, maybe not.  You also have Henshin's Amulets and Scroll Caches to pay for it.  You do lose your Shugenja too, so make sure you're not sacrificing your key guys just to pop a few attackers.

Ugly:  A few cheap shugenja, Bishamon's Fury and Cloak of night can really ruin any Military blitzer's day.

Stranglehold
Ritual Limited: Bow a number of Shugenja Personalities you control, including this one equal to the number of units the target controls: Target a player. Bow all units he controls.

Good: Hey, who wouldn't want to bow out ALL of his opponent's units.   It's not even a battle action, so you can safely remain at home and play the control game.  It doesn't care who your opponent is, who his personalities are, or what they have attached.   They bow.

Bad:  It's a limited action.  So you can stop your opponent from defending on your turn, but you have to have an army left to attack.  Then on your turn, your shugenja are bowed out from the spell and your samurai are bowed out from your attack.  You also have to target ALL of your opponent's personalities.  Therefore, you must either equal or outnumber him (sounds like a box party deck).  The spell even gets around using shugenja followers to cast rituals.

Ugly:  If you can get this combo off, it's game over.  You need: Equal or greater shugenja than your opponent, and Sezaru or Plans within plans.  Lock down his personalities on his turn (plans) or yours (Sezaru), then you attack undefended provinces on your turn.  With a few beefy shugenja or Samurai, this could be a one turn win.

Essence of Yomi
You may, as a Battle action, pay this Spell's Gold cost and discard it from your hand to give +3F/+3C to an opposed non-Shadowlands Samurai. Battle: Bow this Shugenja to give +3F/+3C to a non-Shadowlands Personality or -3F to a Shadowlands Personality.

Good: It's both a spell and a battle action, versatility.  If you're playing KA, it's pretty cheap (only 2 gold), even for a battle action.  If you cast it as a spell, you don't have to be opposed, so you can sneak in there with some cavalry (aka Elemental dragon) or Isawa Moriko someone in to an undefended province.

Bad:  It is ONLY a battle action.  Therefore the +3Chi can't be used for duel protection or Kolat Assassin prevention in the limited/open phase.  It also means that you can't prep yourself to go in battle with increased stats.

Ugly: You can imagine it as a reusable, nonspecific strength of purity.  There is really no jank I see with it except that you can play it out of your hand like a surprise. Oh, big surprise!

Importune Kami
Ritual Limited: Bow this Shugenja and any number of your other Shugenja to raise the strength of each of your Provinces by three times the number of Shugenja bowed until the beginning of your next turn.

Good: Probably the best defensive card the Phoenix have.  If you are trying to honor run, this can be your best friend.  It is luckily one of the rituals that asks for shugenja, not shugenja personalities.  Therefore, bow 2 of your shuggies plus your 2 minor shugenja and BLAMMO +12 province strength!

Bad: It is only temporary, unlike Lessons from Earth.  There is also the Barbarian Wall region now that can quickly reset your province strength.  You might also fear Nimuro.  Then again, Barbarian wall has fallen out of popular use except in Khol and who plays Lion anymore? (just kidding)

Ugly:  As with most Phoenix decks, slap a Sezaru on the table and have at it.  Bow out your, let's say 5 shugenja and 2 shugenja followers to cast the ritual.  Smile at your 27 province strength, then Sezaru to unbow and do it again.  Watch you opponent's military deck cry at your 48 province strength.  Then hope they don't have any meta for it!

Fire and Air
Elemental Battle: Bow this Shugenja for a Ranged 2 Attack.
Elemental Battle: Once per turn, without bowing, move this unit to an adjacent Province.

Good: Most any spell with multiple actions on it is good.  That means versatility and in a game of vastly different deck archetypes, adapting midgame is key to victory.  On the offensive, this spells acts as a miniature Right Hand.  With a decent attacking unit this can be the key to a province.  On the defense, it offer a small but useful ranged attack.  Take out a follower or combine it with a firestorm legion for a more impressive blast.

Bad: The downfall of this spell is it's need to be combined for much effectiveness at all.  Shugenja are not known for their province destroying strength.  Usually a strength 2 attack isn't going to do much but kill a follower, and you're bowing out a shugenja.

Ugly:  You can use this if you're playing your CoR deck vs Unicorn to dodge them early on.  You ca also use this in a nasty, sneaky combo that includes Isawa Toshiji, Shiba Emiri, and this spell.  Send Toshiji (with spell) to province A (2 Force).  Hopefully, your opponent will defend.  Resolve an adjacent undefended battle. Move Toshiji over (2 Force).  Play strength of purity on him (5 Force).  Bow him to move Emiri in with her ability (8 Force).  That should take most provinces.

Suitengu's Surge
Reaction: Before an action targets a unit you control, bow this Shugenja: Remove the unit from the game. Return it to the game, with all attached cards and tokens, before the beginning of the next turn.

Good:  Do I need to explain how saving ANY one of your personalities from just about any ill fate is good?  You also get them back at the end of the turn.

Bad:  You must be targeted.  You are not targeted with Overwhelmed, that kinda hurts a CoR Dragon.  You do lose the unit until the end of the turn, no province taking this time.

Ugly:  Wow the combos that are out there are sick.  I'm not going to list them all, but one of the silliest comes from CoR.  Let's say that it's mid game, you've done pretty well on honor so far and due to its ability, you have three Tengoku acolytes out.  Well, you have decided that you'd rather honor run your opponent and use your Dragons defensively.  Each turn, send one of your Kanjiro's over to the opponent's provinces, alone.  If he does anything to him, send him out with a Surge.  If not, you target him with something.  At the end of the turn, when he comes back into play, react off the three Tengoku acolytes and gain 6 honor, then buy some people out for full.  Rinse, Repeat.


Flames of the Phoenix
Reaction: Bow this Shugenja before a target Personality is destroyed during the Battle Action Segment to negate the destruction. Destroy that Personality when the Attack Phase ends if he or she is still in play.

Good:  In that last desperate bid to take a province, you need all the people you can get.  This helps keep them around.  Again, anything that keeps your people on the table is good.

Bad: Well, they still die.  And not even at the end of the turn, at the end of the attack phase.

Ugly:  Let's use another CoR example, I send over my Air Dragon to attack the Crane.  They defend one personality at each province.  Is that a To Do What We Must I smell or an Overwhelmed?  Anyway, it looks like I'm losing a Dragon, eh?  Nope, I'm going to Flames of the Phoenix him, still take the province and Storm of Isawa him back next turn!


Sapphire Strike
Ritual Limited: Bow this Shugenja and one other Shugenja Personality you control, and destroy this card: Target a bowed Personality. Destroy him.

Good: Again, how much do I need to say that killing a personality regardless of attachments are traits is good.  In a game that is tending towards control this is the ultimate control, dead.

Bad:  Sapphire strike is the ugly, gap-toothed cousin of Touch of Death.  So now I need to bow 2 people to kill 1?  That might be a lot of resources for a shugenja/samurai deck.  Hopefully that means the person you are killing is either a big baddie or the keystone to a deadly combo.

Ugly:  If you are lucky enough to face an opponent with a combo deck, this might help you handle it.  As I write this, there is concern in the environment with Doji Saori.  She bows to have a duelist issue a challenge with annoying results.  Well, when you get the chance, you can Sapphire Strike her.  End of combo.  They can have 3 of her in the deck, you can have 3 Sapphire Strikes in the deck.

Iron Citadel exp
Black Scroll. Shadowlands. Experienced. Unique Limited: Bow and destroy this Shugenja and remove this Spell from the game to permanently raise your Province Strength by 3. Permanently gain "Reaction: After one of your Maho Spells or Maho Kihos resolves, bow your Stronghold to permanently raise your Province Strength by 2." You may not win an Honor Victory this game.

Good:  As we've seen with Importune Kami, increasing your province strength (from 6) is generally a good thing, no matter what your deck does.  This spell is almost exclusively limited to a CoB deck unless you are playing some bloodspeaker MGC or KA.  Chances are that if you're playing a maho deck, you probably won't win on honor anyway.

Bad: It is unique, meaning that even with spell hunting capabilities, unless you are Walking the way, you may have a hard time getting it early on.  You also lose the casting shugenja, but you can alleviate those worries by having someone worthless like Agasha Seruma do it.

Ugly: In a good Maho filled CoB deck, you can raise your province strength by at least 2 per turn, even more if you use Hero's Grave.  This can quickly get you to a level where you can confidently bow out in an attack and a small amount of send home will eliminate an opponent's chance of taking a province.

 

Part II

Fist of Osano-Wo
Elemental Limited: Bow this Shugenja and destroy this Spell to destroy a Holding.

Good: Seeing as gold economy is one of the cornerstones to this game.  Controlling your opponent's gold can be very powerful.  How many times have you lost a game only to exclaim "I got gold screwed!".  If you have a bad gold draw, you might lose no matter how well you deck is constructed.  Why do you think they created Gifts and Favors and A Favor Returned?  This spell allows you to destroy either your opponent's biggest gold production (Pillar of Flesh), or a very useful one (Ki-Rin's Shrine exp, Shi-Tien Yen-Wang Temple).

Bad: For 5 gold, it's a one shot spell that may end up only exploding your opponent's Barley farm.  If it comes out too late, your opponent may laugh off losing one of his gold producing holdings.

Ugly:  Combining 3 copies of this spell with 3 copies of Ebb and Flow and 3 copies of Explosives, throwing in Asako Genjo, you can possibly destroy 15 of your opponent's holdings.  I've played against decks that don't even have that many.  Nasty.


Ebb and Flow
Open: Bow this Shugenja to straighten a bowed Holding. Destroy that Holding the next time this turn it becomes bowed.

Good:  Slightly more versatile than Fist of Osano-wo, you can actually use this on your own gold.  Sure you'll blow it up, but you'll  get gold out of it twice in one turn.  If that wins you the game, it's worth it.  For the rest of the strategy, see the entry for Fist of Osano-Wo.

Bad: If you do use it in a holding destruction deck, keep in mind that your opponent has the opportunity to NOT bow it.  Either pressure him into bowing it or have another card that bows it for him (maybe Embrace the Elements, but that's kind of janky).

Ugly: See the entry for Fist of Osano-Wo.

Inazuma Blade
Weapon. Unique Inazuma Blade is both a Spell and an Item. (Note: this is a +3/+3 spell)

Good: Spell only gold (Henshin's amulet) can pay for it.  Item gold (Roadside shrine) can pay for it.  It gives you Force.  It gives you Chi.  It's a weapon AND a spell.  What else could you want?

Bad:  All it does is add to your stats and give you an attachment.  Not really powerful as compared to other spells in its price range (see Kuro's Fire).  It's also unique so only one of them in the deck.

Ugly:  It works best in combination with other spells.  Slap it on anyone, then attach Kuro's Fire or Fire from Within.  It also allows your shugenja to get some force for province taking or Chi boost for dueling.  You can bow it for Souls in Harmony with no loss of effectiveness.  In an attachment heavy force like the Phoenix have, it helps with "I am Ready".  It also gives you another card to bounce Into the Darkness off of.

Purity of Seven Thunders
Ritual Limited: Bow this Shugenja and any number of your other Shugenja such that their combined Chi is greater than 14, and destroy this Spell and this Shugenja, to destroy all Shadowlands cards. The Shugenja in this Ritual cannot straighten during your next turn.

Good:  If your opponent is Shadowlands, you just won.

Bad: If your opponent is not Shadowlands, it's dead weight.  There is the possibility that Shadowlands players (if they expect this) are packing some anti-spell meta.

Ugly:  As many spells do, this one becomes unbelievable with Sezaru in play.  Step1-cast.  Step 2-Straighten all shugenja.  Step 3- attack all provinces (hopefully you have enough force.  Remember that it says you may not straighten during your next turn.  It says nothing about your current turn or your opponent's turn.  You can probably get off two good, unopposed attack phases because you have probably destroyed most all of your opponent's gold.


The Fires that Cleanse
Elemental Battle: Bow and destroy this Shugenja and destroy this Spell to destroy an opposing Personality.

Good: Well, it's in battle PK.  That's always good.  In the extreme, you can destroy your Agasha Seruma to destroy the opponent's biggest attacker.  It doesn't care about attachments or stats of your opponent.

Bad:  There are ways to stop battle actions and some leave you missing one shugenja and your opponent with all of their people.  This environment is also seeing an increase in redirection, therefore you may not take out who you want.

Ugly:  If you are playing CoR Dragons, you can blow one up to take anyone out, then use Isawa Sachi to place them in your province and buy them back out this turn.  Combo that with Isawa Sueno and some Tengoku acolytes and you have one dead opponent and a crap-ton of honor.

Walking the Way
Limited: Bow this Shugenja and destroy this Spell to search your Fate deck for any one card and put it in your hand.

Good: Toolboxing (being able to go get what you want, when you want it) your fate deck is key to just about any game.  It allows you to put only 1 or 2 copies of key meta cards in your deck and get them when you need them.

Bad: Not really anything bad except you end up with a bowed shugenja, but when don't you?

Ugly:  The look on your opponent's face when you get the killer card can be priceless.  Most other card draw in the game is much more limited.  This doesn't care about focus value, or if you have pulled a copy yet, and it doesn't let your opponent know what the card is.

Force of will
Open: Bow this Shugenja and destroy this Spell to switch the Personal Honor and Chi of a target Personality. If you control the target, you need not destroy this Spell.

Good: The obvious use of the card is to kill someone.  Either find someone with a 0 Chi or a dishonored personality, and Whammo!  Simple and Action phase (less things to stop it and you don't have to be opposed). Dueling is where it's at now.  Are you facing a killer crane dueling deck with one or two massive duelists?  How good would they be with a 2-4 chi?  You can also use it to help your duels.  Many Phoenix have good PH so throw some Show me your stance in the deck.  Boost your personal honor to 5-7 then duel away.  If they become dishonored, you can use the spell on them now!

Bad:  Unless you use it on your own guys, it's a one shot.  It's also not too effective for killing opponents if they all have personal honor above 0.

Ugly:  How about a nice little honor bomb? Have someone in play with a VERY high chi.  Give them an item with a large chi boost (larger than their chi).  The best combo here is Aikune with the Celestial sword, but you get the point.  Cast FoW on them and give them a really low chi and a huge PH.  Bow them an move the sword to someone else.  The ensuing chi loss will kill them.  Either use Isawa Sachi or MGC to get them back in a province this turn.  Buy them out.  Sure they will die instantly from 0 Chi, but if you pay full, you can get their personal honor (which is still frickin' huge!).  I've seen honor gains in the high 20s from this.  If you have multiple Sachis in play, enjoy many copies of this person in one turn.  You could easily get 60-70 honor.  That's why it's called a bomb. 

Speed of the Plains
Elemental Air Battle: Once per turn, without bowing this Shugenja, immediately take two additional consecutive Battle and/or Open actions. If this Shugenja has the Air trait, you may use this action if this Shugenja is not in the current battle.

Good: Very cheap.  You don't have to bow.  Your air shugenja and Chieh exp don't have to be in the battle.  The effects chain nicely.  Cast three of these puppies and end up with 4 more consecutive actions. 

Bad:  If you don't have a lot of battle actions to take, it's dead weight.  Make sure that your deck can use it to its full effectiveness.

Ugly:  Head over to your opponent's provinces.  Let him defend against you.  Drop a sneak attack, cast three speed of the plains.  Action 1-Kuro's fire, react Isawa house guard.  Action 2-Kuro's Fire, react Isawa House guard.  Action 3-Kuro's fire.  Action 4- whatever the heck you want at this point!