Betty Grof

Betty Grof (voiced by Felicia Day) was a human-turned-wizard woman revealed to have once been the fiancée of a man named Simon Petrikov, who would much later become the Ice King. She and Petrikov were in a committed relationship until Simon obtained an enchanted crown, which gradually began to alter his body and warp his mind.

In the series finale, "Come Along With Me," Betty is consumed by GOLB with Ice King and Finn. She and Simon are reverted to their original human forms from the deity's "digestive" process. Remaining inside while the others escape, Betty uses the Ice King's crown in its wish-granting state to protect Simon and sacrifices herself, making her and GOLB fuse into one being.