After destroying the sealed door jump onto green Power Plate.
Use other powers to get onto a wooden platform and from there run in the direction of another green ring.
You will be move to a place where the battle will take place. The Warrior is not sensitive to your attacks so you need to trick him. Stand on the edge of the arena in a place where there is no slime and let him attack you. Run around the Warrior and push him into the chasm.
Platform made of stone will collapse and you will fall down. This not the end of the fight.
The Warrior will come back but this time he will be in flames like a live torch. Don't attack him, go back all the time and run away from him. After a will his health bar will reach zero and as a result he will be defeated. Go to a green ring.
Jump onto the Power Plate which will move you to a collapsing wall. Start running straight ahead on the wall.
At the end start sliding. As a result you will run away from endangered area.