Skullma

A Grim-Reaper style monster with a scythe and assisted by two hornless versions of himself, Skullmastars. He played a part in Kotaro's rebirth into Black RX, killed by him while the Skullmastars live on to serve the Crisis Empire on different occasions. Skullma returned in the Kamen Rider Black RX movie to fight Kotaro before he was sucked into a dimensional warp. Episodes 1-2, 45 and Movie