I was recently playing a game of nethack and I was doing really good, and decided to go up to sokoban. I was walking around when suddenly some Hill Orcs spawned and I was able to take them out, and they didn't seem to spawn that close, but soon afterwards, an ant that seemingly came out of nowhere killed me in one hit with a poisoned bite. The ant seemed to just appear right next to me, but it probably just moved diagonally from behind a boulder that was next to me. Even if that's the case, it still spawned pretty close to me. I've also had other instances where somewhat strong/exotic monsters spawned on sokoban. So i was wondering two things:
1) Why do the enemies spawn so close in sokoban?
2) Why do different/stronger enemies spawn on sokoban? Since I'm going upwards and the Dungeon Level is decreasing, shouldn't the monsters spawning be weaker?