Diablos as it appears in Revenant Wings.

Diablos is a recurring summon featured in the Final Fantasy series. In the video games, his attacks are primarily gravity based. It originally appeared in the PlayStation exclusive Final Fantasy VIII, though since then it has appeared in a couple of Nintendo titles including the Final Fantasy VI Game Boy Advance remake (where it appeared under the name of Diabolos), and Final Fantasy XII: Revenant Wings for the Nintendo DS.

In the GBA remake of VI, Diabolos would become a summon after you defeated the Kaiser Dragon.