I recruited this demon very early in the game. It had an attack called Lost Word that I used once and automatically killed all the other demons in my party. I was wondering, is this really its only use? It didn't even do any damage to the other enemies I was facing.
According to the Megami Tensei Wiki, the "Lost Word" magic skill can be used by Garuda, Huangdi, and Nemechi Knocker.
It will randomly do one of 4 effects: