Create a Blue Mage Spell!

[Auryan]

More spells! Time to get a little naughty.

Auto-Ribbon - Self-use only. Renders the blue mage immune to most status ailments (excluding Death and boss specific status effects).
Note: This ability is not a usable spell, but rather a support ability that will always be active if the BLU has it equipped. Downside is that support abilities will take 3 slots instead of the usual 1 that the other spells take.
Source: Masked Carnival after learning a number of spells and completing the higher fights

People are so going to troll with this next one, but I like the idea of friendly fire spells. Maybe it'll be just too toxic, but here goes.

Mega-Graviton - Shadow-aspected spell that affects friends and foes alike. Reduces targets HP to 60% of max HP and place several status ailments on all targets within the radius. Status effects include: Slow, Sleep, Silence, Blind and Doom.
Source: Masked Carnival fight featuring Cindy, Sandy and Mindy from FFX. I would like this fight to be one of the last, if not the last, of the newer additions to the carnival and put several achievements and glamour rewards around it. Magus Sister gear, mount and title.
Cast time: 3 seconds
Mana cost: 60% of the caster's maximum MP

I want to make this one a really nasty, canon-like spell with some drawbacks and theory crafting around it.

Copycat's Grudge - Shadow-aspected spell that deals damage to a target based on the amount of blue spells learned and equipped. Will deal more damage with more spells learned and more damage with LESS spells/abilities equipped. For example: the spell will deal 100% more damage if the blue mage has only 12 spells equipped. Percentage is subject to change.
Source: Queen Tonberry
Cast time: 1 second
Cooldown: 2 minutes, not on global cooldown

[Vanitas]

D.A.B.
Source: Queueing as DPS
Deals 50000 potency to any enemy and uninstalls the game from your hard drive.

[Bonbori]

I'd love to eventually be able to use some of Tsukuyomi's abilities. Nightfall would probably lend itself best to being converted into a playable spell.

Lead of the Underworld: Randomly targets a nearby enemy and unleashes a powerful line attack, dealing unaspected damage with 1000 potency split between all affected enemies.
Source: Tsukuyomi (Castrum Fluminis, Minstrel's Ballad: Tsukuyomi's Pain)
Cast time: 2.5 seconds
Cooldown: 180s (shared with Steel of the Underworld)

Steel of the Underworld: Randomly targets up to 3 nearby enemies and unleashes a powerful cone attack at each of them in quick succession, dealing unaspected damage with 100 potency and inflicting a stack of Nightfallen (up to a maximum of 2). Each stack of Nightfallen increases the damage suffered from subsequent Steel of the Underworld strikes by 100%.
Source: Tsukuyomi (Castrum Fluminis, Minstrel's Ballad: Tsukuyomi's Pain)
Cast time: 2.5 seconds
Cooldown: 180s (shared with Lead of the Underworld)

[Kalise]

Moar Spells!

Gil Toss - Costs 10% of your Gil to cast. Deals damage equal to the amount of Gil consumed to target.
Source: Whalaqee Totem

100,000 Needles - Deals a fixed 100,000 damage which is shared by all enemies around you.
Source: Sabotender Emperatriz

Golden Tongue - Increases magical damage dealt by 30% for 30s
Source: Puddings

[Zsplash]

I like the blu jokes

Limited Development:
This attack has a potency of 1 with a cast time of 51,840,000 seconds (600 days).
If you do manage to finish the cast, it will fail and explode. Side effect of cast is to attract random onlookers to praise your efforts even if ultimately pointless.
Cooldown of 1 hour, afterwards the ability is removed from your bar as it's been completely forgotten by the user.
Source: The souls of orphans

[Singularity]

Ballistic Missile
(Ground placed AoE)
If exactly two enemies are hit by the AoE, inflicts death on both of them.
Source: The Avatar

Compress
Deals damage with a potency of 30 to all enemies in a straight line before you and inflicts the mini status.
Source: Construct 7

Also, being a caster, it needs an AoE LB3
Aetheric Profusion
Deals damage with a potency of 5000 to all enemies in the targeted area.
Source: Twintania

[Khalithar]

I want a spell like Hello, World from o12s. Let’s see the raid boss have to deal with a bunch of mechanics in a sequence for a change! Then if the bosses messes up he takes the 999,999 damage.