A leader-like Kaiju that rules over all others. Geronimon has the ability to revive any Kaiju that has been defeated in the past, attacks its enemies by launching its feathers, controls them with brainwaves like missiles, and emits a gas that causes targets to levitate into the air.

Geronimon planned an all-out attack on Ultraman and the SSSP by reviving over 60 Kaiju they had defeated. Concealing itself in Mt. Oiwa, Geronimon first revived the Subterranean Monster Telesdon, the Comet Monster Dorako, and the Friendly Monster Pigmon.

However Pigmon, a human friendly Kaiju (Revived), reported Geronimon to the SSSP, ruining its secret plan. The SSSP arrives at Mt. Oiwa and defeats the Telesdon (Revived) and Dorako (Revived), at which point Geronimon shows itself.

When Ultraman arrives to fight him, it fires its tail feathers at him, but Ultraman shoots them down with his Spacium Beam. In the end Geronimon is held into the air as Ide fires at it with his latest invention the Spark 8, causing Geronimon to explode.