So I generate a new world, hoping for a Necro Tower to assault and to become a necromancer for the first time. I get my wish and waltz in to the tower, smashing my way to the top and defeating all the necromancers and zombie hordes without a scratch (my companions, however, were not so lucky). After learning the secrets of life and death and raising a few zombies, I find that I cannot descend any floors. The staircase to my right leads up, and I can traverse up and down that one with no problem, but I just can't go down the staircase that leads out of the tower. The only odd thing that I've noticed is that it appears to have not only a floor hatch but also a hatch cover.