Restore HP at regular interval
Regen is a restore magic spell in Final Fantasy VIII. The spell is used to apply the Regen status effect on a target, causing their HP to gradually restore over time. The spell can also be junctioned to boost stats, especially HP.
Regen is easily refined from Mesmerize Blade using Siren's L Mag-RF ability, as it is relatively easy to obtain from Mesmerize enemies either by mugging, dropping, or from using Card Mod on their cards.
Regen when cast will apply the Regen status effect, which will restore 5% Max HP every 80 x BattleSpeed ticks (a tick is a 1/60th of a second), resulting in the status restoring 80% max HP over the course of around 21.3 seconds (16 times per cast). It can also gradually damage undead enemies.
Regen provides considerable boosts to many stats when junctioned, namely HP, for which it provides a greater boost than even Curaga. It also provides among the best boosts for Vitality and Spirit.