I had no idea the "you sense powerful magic" message meant there was a superweapon on that floor. I must've passed so many of them, untested for fear of curses...

I'm not that great at this game. The farthest I've gotten was to floor 20, where I died as a Warlord. How exactly does experience work, especially in regards to wraiths knocking you down levels? Do they steal exp too? In levels, say, 15+, should I be saving scrolls of enchant/vorpalize for something...