After watching the demon land gate erupt from the ground you will need to go back outside the keep.
Go to the lock east gate at the bottom of the ramp to see it explode with new enemies.
Kill them and then go back up towards the keep, and go through the gate to the west. Follow the path to eventually right a huge red demon with an axe. You can avoid this fight and get the sword from behind him, but beating him get you another cheev.
Return to the keep and the busted east gate, and place the sword in the stone. Once you go through the gate, the cheev will pop.