Sacrifices caster to completely restore an ally's HP and MP.
Transfusion (融合, Yūgō?, lit. Fuse), also known as Pep Up, Fuse, Fusion, and Merge, is a recurring ability in the Final Fantasy series, most commonly used by Flan-type enemies. It generally restores all HP and MP to the party at the cost of removing the user from the battle.
The Blue Magic Transfusion, or Pep Up, kills the user, and the chosen target fully recovers his/her HP and MP. It cannot be reflected. If the caster of the spell is also its target, the caster dies, but recovers all of their MP. It costs 13 MP to cast. It can be obtained from the enemies Mythril Dragon, Calcruthl, Birostris, Devilfish, and Mover, as well as the boss Gargoyle. The player may utilize this ability by catching and releasing a Devilfish or Birostris.
Fully heals an ally at the cost of the caster's own life and all MP.
Strago can learn Transfusion, also known as Pep Up, and it costs 1 MP to cast. It removes the user from battle permanently, but restores HP/MP to the chosen target as well as removing all negative statuses except KO and Frozen. Transfusion can be learned from Intangir, Junk and Mousse.
Flans can use Merge to fully heal the HP of a target at the cost of being KO'd.