Demonic, Daunting, Dreadful and Purple (I know it would be William who is properly "Purple" but Springtrap is better).

Two devilish beings of pure EVIL meet face to face.

While their supernatural powers are minor in some cases, their intelligence and tricky nature are their most dangerous weapons.

In simple, both come from their own game series that relates to death, souls, and coming back to life, as well as both being purple and stealthy.

This is kinda funny