From the entrance to the room, the lever for the far left chamber is just to the right of it, while to lever for the far right chamber is to the left (both sticking out of the floor). Check out this video, starting just after the conversation ends:
Divinity 2 - Ch54-03 - BOSS: General Raze. In this
German video of the fight in Ego Draconis, the levers needed to be pulled several times, due to not enough damage being done to finish off the general before the regeneration chambers reactivated.
