Killbus (キルバス, Kirubasu) is the main antagonist of Build NEW WORLD: Kamen Rider Cross-Z. He was the former overlord of the Blood Tribe who initially took on the appearance of Sento Kiryu (桐生 戦兎, Kiryū Sento) and Kamen Rider Build (仮面ライダービルド, Kamen Raidā Birudo) before preferring Satoshi Kakizaki (柿崎 悟志, Kakizaki Satoshi) instead, later becoming Kamen Rider Killbus (仮面ライダーキルバス, Kamen Raidā Kirubasu) himself.