How I think the Lantern should work...

How I think it should work... You could either:

Press the normal entrance without glancing at the lantern. The lantern doesn't affect the area. Basically normal mechanics, and no corpses.

Activate the lantern, which gives you this:
You should get X upsides and Y downsides, both X and Y being a random number in the range 1->Z/2, where Z is the number of different mob types, rounded down.
The mobs should not be ordered in any way, should either be alphabetically or random.

That would make this mechanic work! As it is, it is not much fun...