OUAT/VD/Originals: Former Enemies United (Klatherine)

Set in OUAT S5 and Originals after 5x13, as well as after VD. Kat ends up in the underworld after sacrificing herself, since she believes Hook doesn't deserve to die for a mistake she made, trying to save Rumple from losing the last of the light in his heart. Klaus ends up there after sacrificing himself with Elijah for Hope. When he finds Kat injured from Cerberus' poisonous bites, can he get them out of there in time for Rumple to go on a rescue mission? Will Klaus be able to kill it? Will Kat survive? What will ensue between Kat and Klaus?