GuldThunder (ガルドサンダー, Garudosandā) is a red Fenghuang monster in a Phoenix-shaped helmet. It can attack with its retractable tail and use fire attacks. It devoured Yuichi Saito under Kanzaki's orders when Yuichi turned down Kanzaki's offer. It was later used by Kanzaki to attack Kamen Rider Raia. It was later destroyed by Raia's Hide Venom. It is also the Contract Monster of Yuichi in concept art, representing a hypothetical situation in which he accepted Kanzaki's offer. In the World of Ryuki,
