Beast Soul: Belcusas

Beast Soul: Belcusas (ビーストソル・ベルクーセス Bīsuto Soru Berukūsesu) is an anime-only, Take Over Spell.

Description
The user transforms their body to that of Belcusas the Thunderclap, an enormous, heavily-armored, and physically powerful creature that Rustyrose imagined into existence to fight on his behalf.