Prismo had teleported you to the world of Farmworld Fionna to prevent her from traveling through the multiverse to cause chaos, when you arrived at Farmworld, Fionna was distracted with something, so you would quickly go for the Enchiridion and when you were going to take it, you would see no more no less than the Lich...

the Lich was controlling the body of Fionna's cat, the Lich would see you and quickly take on a muscular, but feminine form and run towards you

Cake (lich): STOP HUMAN!!