The Demon doesn’t have much new in terms of attacks. It can use a basic attack, Tyrfing (double-powered attack), Firaga, Aero, Southern Cross, Flare Star, Meteor, Metal Cutter, and Stop. People afflicted with Stop soon with get killed by Blaster.
Begin with Stop on the enemy, then toss up Hastega and Mighty Guard (or somehow put Shell on all). Then continue to batter the Demon with various things – Blizzaga, Thundaga, Flare, Meteor, Ultima – while keeping it in check with Stop.
After the battle, go north to the Save Point. Use it! Then drop down into the hole to the north. After landing, step on the switch and swap to…
If you’ve followed the walkthrough, you should still be on the switch. Go south and through the door, then west to return inside. Go north and through another door. Go north through yet another and go north some more. At the statue, heal and prepare for another fight. So many bosses!