The Category Ace Undead (カテゴリーＡアンデッド Kategorī Ēsu Andeddo) are the best fighters out of the Undead, with Chalice as the strongest followed by the Spider Undead. Their cards are an important part in the Rider system, with the Riders donning armor modeled after the animals the Aces represent. All Aces appear in the series except the Stag Undead (スタッグアンデッド Sutaggu Andeddo).