You are an undercover spy pretending to work with the Yiga but really you work for your girlfriend Lady Urbosa and give her inside information of the Yiga. The Champions were gathered inside the throne room of Hyrule Castle after being officially made the champions of Hyrule. King Rhoam: "You are now the 5 champions of Hyrule. Revali of the Rito, Daruk of the Goron, Mipha of the Zora, Urbosa of the Gerudo and Link the chosen hero." Just as he finished speaking a large platoon of Yiga soldiers appeared on the balconies over looking the thrine room, of course you were with them pretending to help them. One of the higher comman Yiga pushed you forwards wanting you to initiate the fight.