Blind him.

While he's busy thinking out loud about what to do with you, you cast a Shadow Trick on him, relieved to find that its cast time is almost instant. His eyes turn black with a small burst of black mist, and he straightens up in surprise, looking around at nothing as he tries to figure out what just happened. You use those precious seconds to climb out of the chest and run past him to the nearby door. The doorknob is above comfortable height, but it's not as high up as the boss door and you reach it with your first jump, opening the door and slipping outside.

Meanwhile, the necromancer has figured out what happened and is fumbling around, trying to follow the sounds of you. You close the door behind you to buy you a little bit of time, and run while he walks into the door and proceeds to look for the doorknob.

You quickly arrive at a spiral staircase. Your legs are not made to walk up or down such large steps, and that mixed with your hurry causes you to fall all the way down. Ignoring the minor HP loss, you keep running until you find what looks like a dead end. However you see a lever at the wall, and try to reach for it. It's even higher up than the doorknob to the boss door, and you're quite sure that even if you weren't under severe time pressure you couldn't reach it. Then you remember... You got some items now. You take off your amulet, and while holding the gem you make another try.

You manage to coil the string around the lever, and pull it down. The wall of the apparent dead end slowly slides out of the way, and you step outside to find yourself in a relatively large chamber with a few pots and bones as the only decoration, a corridor leading away from it and a door on the opposite side. It looks different from the other doors in the dungeon, but not fancy like the boss door.

You realize where you must be. This has to be the first room in the dungeon. And that door... is the exit. It makes perfect sense. Once the heroes have beaten the boss, they get a shortcut back to the start so they don't have to backtrack all the way. Which means that door leads to freedom.

As soon as this dawns upon you, you sprint towards it faster than you ever have. Faster than you have ran from any hero. Which makes it all the more painful when you run into The Keeper again, as he drops down from the ceiling. Had you ran any faster he would have landed on top of you and probably ended you then and there. Of course, as you quickly back away and gaze up at the great stone warrior, his blue eyes staring down at you, you think to yourself that you're not much less fucked now than you would have been.