[Autumn]

Spellthief hasn't gotten a lot of new DLC in a little while and has been kinda left in the dust, I think introducing a few new-ish monster spells to its possible spell repetoire could make things more interesting for them, not every single one of them has to make it in of course, and possibly you could place restrictions on them for players specifically which I'll also mention, but here's what I'd possibly consider making stealable for spells:

Ominous Spell (Changed to magic)- Currently heals for 500 HP and provides LV/3 as all bonus stats to the Ice Giant that casts it after a set amount of turns
-If a player uses this ability, the LV is capped to 10 EDIT: the heal is halved as well.

(I also just love the idea of players being able to turn HUGE after the cast goes off, this is countered entirely by a single null like requinite or shells or wash away etc.)

Self-detonate - When adjacent to an enemy, destroys self to deal Fire magic damage to all within a 3 Range circle equal to level + 500% of Fire ATK. Requires a certain number of turns to pass before it can be used.
-If a player has this ability then a 5 round cooldown will be put into place at the start of the match, yes it would kill the player too, possibly have damage cap out at player LV*10 or current health (whichever is lower) so you don't reach scenarios where this deals over 600 damage.
(Please let me chiaotzu someone.)

Chilling Howl - Unleash a freezing roar. Enemies in a 2 Range circle take Ice magic damage equal to 150% Ice ATK It can also inflict Frostbite LV X (X = 10 or LV/2, whichever is higher) for 3 rounds.
-100% SWA scaling should be added so it does decent damage

Banshee Wail - Unleash an ear-piercing scream. Enemies in a 2 Range circle take Sound magic damage equal to 150% Sound ATK. It can also inflict Fear for 3 rounds.
-100% SWA scaling could be added for more damage, Domino Resonate already does this better so may as well.

Denile - Fires its own jam at an enemy within 3 Range who is enchanted with an elemental, dealing Water magic damage to them. Also seals Elemental Impacts and certain elemental enchant effects for 3 rounds.

Howl And Haunt - Roar at a target within 4 Range, inflicting them with Hunted LV X (X = 10+25% of level) and gaining Quickness LV 5 for 3 rounds.

Demon Drool - Spits a vile, demonic acid towards the target in a line. The first enemy hit by the projectile takes Dark and Water damage. It can also Poison the target randomly.

Immolate - Changed to magic.

Angler Light - Changed to magic.

Thunderclap - Changed to magic, FP cost lowered to user's LV/2 (currently equal to LV)

Railgan - Allowed to be stolen from Beetles.

Anything I didn't comment on specifically is probably more than fine for players to have access to, I just want to have a blue mage plz

[K Peculier]

I approve of all of these since they're not too crazy. Alot of monster skills could just have mini player versions in all honesty, without breaking metas too badly.

I think the heart of spellthief, especially now that we have cooldowns between each stolen spell is that they should have a variable of neat and suprising abilities rather than damage, damage, damage like it was in the past with certain combos.

I sometimes wish spell steal got an extra 2 spells to steal ever since the cooldown nerf. (Hint hint, nudge nudge)

(I also want to chiaotzu someone too.)

[Slydria]

I definitely approve of giving Spellthief some more toys to play with.

I'd like to suggest Acid Shock (the Beta skill) be considered for stealing since Acid is still a pretty niche element.

Perhaps also a new passive for Spellthief that improves the damage of spells stolen from monsters (say 15%) and lowers the cooldown of them to 1 round instead of 3 rounds (excluding anything that already has a longer cooldown innately) but prevents them from casting any stolen spells that don't come from monsters.

[Autumn]

I think that sort of thing would be pretty unique to Spellthief itself, also improve on their lower damage than player spells somewhat often.

Looking back on this thread I don't think all of these would need to be added, but they definitely are in there for suggestion still..

[Snake]

Please don't let it die here. The Blue Mage dreams... ;_;

[Shujin]

I also like slys suggestion, about monster-mancy skills to be able to use a bit more frequently. I would even be fine with it just being a main class thing.(the CD reduction, that is.)

Generally blue mage, is cool mage. So more options are always welcome.

[Haunted Evil Pajamas]

As a blue magic enthusiast, I support this 100% as spellthief is one of my favorite classes.

[Swiftkusura]

I'd honestly laugh if a ghost/ST used self detonate and last chances and someone just, flicks them to kill them.

[Autumn]

I would still love it if I could run around as a monster-scholar/blue mage enthusiast at some point, I get the fear for spellthief DLC but perhaps with Sly's suggestion you could limit ANY monster spell to being only accessible by a certain passive within Spellthief, I think there is a legit case to be had for opening diversity in roleplay and builds.

[Perdition]

Phenex spellthieves running around self detonating and reviving with passive sounds really funny. In all seriousness, cool ideas all around. Detonate would definitely need to self inflict certain defeat tho.