Since 幻獣 (genjuu) isn't a simple term, and I like the way it sounds, I left it untranslated. The meaning does deserve an explanation, though. 幻 most likely means, in this case, something so incredibly rare that it's simply not realistically possible to prove either that it does or that it doesn't exist, something like "fabled". 獣 means "animal" or "beast", and probably refers mainly to the fact that they aren't human, but this doesn't mean they aren't sentient or intelligent.

裁きの雷 in kanji.

25 MP. Unblockable Thunder magic damage to all enemies (both sides) at 50 power. Power to cost ratio is 2.000.

Thundara has about 20% more power and costs 3 fewer MP to cast, but can be blocked, reflected, or sealed, and can't hit enemies on both sides when surrounded.

18 MP. Sets 'regenerate' status on all allies (both sides). Unblockable.

No truly comparable spell effect. Casting Regenerate four times (assuming a full party) comes the closest, and would cost 40 MP total, take more time, and could be reflected or sealed.

16 MP. Sets 'silence' status on all enemies (both sides), 136 hit rate.

No truly comparable spell effect. Casting Silence on each enemy comes the closest, and would cost 8 MP per foe, take more time assuming at least two foes, and could be reflected or sealed. The spell also has less accuracy, though not by enough to matter except against targets with some magic evade.

28 MP. Sets 'confusion' status on all enemies (both sides), 128 hit rate.

No truly comparable spell effect. Casting Confuse on each enemy comes the closest, and would cost 8 MP per foe, take more time assuming at least two foes, could be reflected or sealed, and is less accurate. But why bother with magic at all? Edgar's Blast Voice costs nothing, works repeatedly in a single battle, and never misses except against immune targets. Its only downside is that it can't hit enemies on both sides when surrounded.

地獄の火炎 in kanji. On a side note, Ifrit is the only Genjuu to animate when summoned.

26 MP. Unblockable Flame magic damage to all enemies (both sides) at 51 power. Power to cost ratio is 1.962.

Fira has about 20% more power and costs 6 fewer MP to cast, but can be blocked, reflected, or sealed, and can't hit enemies on both sides when surrounded.

27 MP. Unblockable Ice magic damage to all enemies (both sides) at 52 power. Power to cost ratio is 1.926.

Blizzara has about 20% more power and costs 6 fewer MP to cast, but can be blocked, reflected, or sealed, and can't hit enemies on both sides when surrounded.

30 MP. Cures all allies (both sides) of 'darkness', 'poison', 'petrified', 'silence', 'confusion', 'slip', 'sleep', 'slow', and 'stop' status. Unblockable.

Esuna removes the same statuses, so this has the same effect as casting that on each ally. Since Esuna costs 15 MP, summoning Unicorn works out at least as well when two or more allies need bad status lifted. The spell can also be sealed, though it ignores reflect just like the summon does.

44 MP. Unblockable magic damage to all enemies (both sides) at 55 power. Power to cost ratio is 1.250.

Each of the standard -ra spells has about 10% more power and costs about half the MP to cast, but can be blocked, reflected, or sealed, and can't hit enemies on both sides when surrounded. Bio has about the same strength and costs 40% less, but, again, can be blocked, reflected, or sealed, and can't hit enemies on both sides when surrounded.

Chaos Wave's neutral damage also means it can neither suffer nor benefit from elemental affinities. The only non-elemental attack spell that doesn't ignore defense, Drain, doesn't make for the best comparison since it's single-target only and isn't a purely offensive spell, but here goes: Drain has about 70% of the power of Chaos Wave (assuming the caster is hurt enough for the full effect, and that Chaos Wave is cast to a single target), but costs about a third of the MP.

悪魔の瞳 in kanji.

45 MP. Sets 'petrified' status on all enemies. 96 hit rate, just low enough to infrequently miss on its own. It will also automatically miss targets immune to instant death, and stamina can block this as well.

No truly comparable spell effect. Casting Break on each enemy comes the closest, and would cost 25 MP per foe, take more time assuming at least two foes, and could be reflected or sealed. However, those factors aside, Break has better accuracy, especially if the target has any magic evade, though accuracy has no effect on stamina blocking.

38 MP. Sets 'transparent' status on all allies (both sides). Unblockable.

No truly comparable spell effect. Casting Vanish four times (assuming a full party) comes the closest, and would cost 72 MP total, take more time, and could be reflected or sealed.

ルビーの光 in kanji.

36 MP. Sets 'reflect' status on all allies (both sides). Unblockable.

No truly comparable spell effect. Casting Reflect four times (assuming a full party) comes the closest, and would cost 88 MP, take more time, and could be sealed, or... well, reflected, but why cast it when it's already in effect?

50 MP. Unblockable Water magic damage to all enemies (both sides) at 58 power. Power to cost ratio is 1.160.

Each of the standard -ra spells has slightly more power and costs less than half the MP to cast, but can be blocked, reflected, or sealed, and can't hit enemies on both sides when surrounded. Regardless, Bubble Blow's primary advantage comes from the inability of any normal spell to inflict Water damage.

33 MP. Golem will block upcoming physical attacks against allies until the total damage blocked exceeds the caster's current HP at the time of casting, only blocking strikes that would otherwise have hit (meaning that characters can still block and dodge on their own without counting against the amount negated).

No comparable spell effect. Earth Wall is something unique, and can be a useful way to avoid physical attacks without having the increased vulnerability to magic attacks that comes with 'transparent' status. Not as useful as in Final Fantasy 5, if only because of the once per battle limit.

30 MP. Sets 'shell' status on all allies (both sides). Unblockable.

No truly comparable spell effect. Casting Shell four times (assuming a full party) comes the closest, and would cost 60 MP total, take more time, and could be reflected or sealed.

40 MP. Recovers HP to all allies (both sides) at 18 power, 80% stronger than Cure. Damages undead, ignores defense, unblockable. Power to cost ratio is 0.450, defense-ignoring.

Cura is vastly superior in most situations, healing over 50% more for just 5/8 of the MP. The only reasons to use Angel Feather, other than hitting allies on both sides when surrounding the enemy, are that it can't be reflected or sealed, but that's what items are for. Why does it not have even twice the effect of a simple Cure spell when it costs eight times as much? Would it have hurt to make it stronger or cheaper, or maybe give it a useful side effect?

61 MP. All allies (both sides) take to the air as with the Jump command. Incidentally sets 'hide' status. Unblockable. Fails on allies with 'stop' status (and probably certain others).

No comparable spell effect. Outfitting everyone with Wyrmknight's Boots has a vaguely similar result, sort of.

Strange things happen if a confused character summons Quetzal. Because of the reversed targeting, it makes all enemies Jump, but only the caster appears to do so, despite not actually Jumping. Other oddities can result from this as well.

70 MP. Sets 'decoy' status on all allies (both sides). Unblockable.

No comparable spell effect. Hardly anything sets 'decoy' status at all, and though somewhat unreliable, it at least it doesn't come with the inability to avoid magic attacks that 'transparent' status does.

68 MP. Unblockable Flame / Ice / Thunder damage to all enemies (both sides) at 110 power. Power to cost ratio is 1.618.

Each -ga spell has about 10% more power and costs about 3/4 the MP to cast, but can be blocked, reflected, or sealed, and can't hit enemies on both sides when surrounded. Additionally, priority for elemental modifiers makes Tri-Disaster's multiple elements a liability. If the target absorbs, nulls, or halves any of them, then the modifier most beneficial to the target takes precedence. The only time it's a good thing for the attacker is when the target is weak to at least one element but doesn't absorb, null, or halve any of them; the attack then inflicts double damage... but then you'd normally do better to just cast the -ga spell of that element. And no, multiple weaknesses don't stack, so no 8x damage on triple-weak enemies.

40 MP. Unblockable Earth damage to all enemies (both sides) at 93 power, between -ra and -ga spells. Unlike Quake, it doesn't ignore defense, but it also doesn't target allies. Always misses targets with 'levitate' status. Power to cost ratio is 2.325.

Except for costing 20% less and not targeting allies, Earth Surround looks like a joke next to Quake, which has nearly 20% more raw power and ignores defense on top of that, generally resulting in far more disparity in damage than the power difference suggests. Throw on some Earth Garb (Gaia Gear) when casting Quake, or just cast Levitate to avoid it. It would be nice if the summon at least hit flying enemies to make it worthwhile, but no, it doesn't.

魅惑の抱擁 in kanji.

74 MP. Recovers HP to all allies (both sides) at 34 power, 3.4 times stronger than Cure. Damages undead, ignores defense, unblockable. Power to cost ratio is 0.459, defense-ignoring.

Curega is vastly superior in most situations, healing nearly twice as much for little more than half the MP. Even Cura, the least efficient healing spell, has over 80% of the power for scarcely a third of the cost. The only reasons to use Alluring Embrace, other than hitting allies on both sides when surrounding the enemy, are that it can't be reflected or sealed, but that's what items are for. Whose idea was it to make the healing summons so overpriced and underpowered?

聖なる審判 in kanji.

90 MP. Unblockable Holy damage to all enemies (both sides) at 114 power. Power to cost ratio is 1.266.

Holy has only a bit less power and costs less than half the MP, but can be blocked, reflected, or sealed. Holy Judgment also has the benefit of hitting multiple enemies, though it halves the base damage to do so.

転生の炎 in kanji

110 MP. Removes 'incapacitated' status and recovers 1/4 max HP (ignores defense) to all allies (both sides). Kills undead targets. Unblockable, but misses all undead targets with 'incapacitated' status and all non-undead targets without 'incapacitated' status, displaying as blocked when the target has a shield that enables spell blocking animations.

No truly comparable spell effect. Raise costs 30 MP and recovers 1/8 max HP, while Araise recovers all HP but costs 60 MP. Each only works on one target at a time and can be sealed. Overall, the standard reviving spells are more economical, but Flames of Reincarnation can make for a great comeback if most of the party goes down when a survivor happens to have Phoenix equipped (or lucks out with a Magicite Shard).

I think I recall Phoenix having a chance of randomly activating (once available) when everyone falls in at least one other Final Fantasy game, but that doesn't happen in this one.

斬鉄剣 translates to "iron-cleaving sword". A weapon obtained in the same general area has the same name.

70 MP. Sets 'incapacitated' status on all enemies (both sides), dropping HP to 0. Delays dying counterattacks when it succeeds, which usually means canceling them outright. Stamina can block this. Accurate enough at 100 hit rate to always hit targets with no magic evade, unless stamina blocking prevents it and except for targets immune to instant death.

This is essentially the same as Dejon (53 MP), but can't be sealed, has better accuracy against targets with any magic evade, and hits enemies on both sides when surrounded. Accuracy has no effect against stamina blocking. Raideen's True Zantetsuken has a still higher accuracy, but is still stamina-blockable and costs 10 more MP.

86 MP. Unblockable defense-ignoring magic damage to all enemies (both sides) at 92 power. Power to cost ratio is 1.070 defense-ignoring.

Ultima costs 6 fewer MP and has over 60% more effect. On the other hand, Ultima isn't exactly easy to come by, and can, amazingly enough, be sealed. The only other comparable spell is Meteor. Megaflare does favorably in this comparison, dealing over 2.5 times the damage for under 1.5 times the cost.

6 MP. May turn one enemy into an item, though it may just miss. The items available and difficulty of morphing depend on the enemy. You can use Gogo's Mimicry to keep trying, as long as no other character takes any other action in the meantime.

Metamorphose is sort of like Death with a bonus, but uses a much, much different method to calculate success rate ( Death can be reflected or sealed and involves MEvd and stamina, while Metamorphose depends only on a hidden "morph value" determined by the monster type), so it makes little sense to compare them.

天地崩壊 in kanji, more literally "collapse of heaven and earth".

96 MP. Unblockable magic damage to all allies and enemies (both sides) at 190 power, more than 50% stronger than -ga spells, full damage against multiple targets. Power to cost ratio is 1.979.

Cosmic Breakdown has considerably more power than any learnable spell that defense affects. Compared to Holy, it causes about 1.75 times the damage, for 2.4 times the MP cost. Compared to standard -ga spells, it has about 1.55 times the power, for about 1.85 times the MP cost. Keep in mind that while it can't be blocked, it also doesn't ignore magic defense (unlike Meteor, Quake, Flare, Melton, Ultima, and Bahamut's Megaflare), making it less impressive than it might be, especially against tough opponents. And, of course, don't forget that it harms allies as well as enemies.

80 MP. Sets 'incapacitated' status on all enemies, dropping HP to 0. Delays dying counterattacks when it succeeds, which usually means canceling them outright. 140 hit rate, but stamina can block this, and targets immune to instant death are unaffected.

This is essentially the same as the 70 MP Odin summon Zantetsuken, but has better accuracy against targets with any magic evade. Accuracy has no effect against stamina blocking. Cayenne's Sever ignores stamina blocking and has an even higher accuracy, but only hits one side when surrounded and, more importantly, suffers from an ungodly wait time.