That’s not even the worst of it. There is a chance through no fault of your own to fall into a pit. That pit might be lined with spikes for extra damage. Those spikes have a chance to be poisoned and without resistance, could be instantly fatal.
ADOM (Ancient Domains of Mystery) is also rife with this, where originally monster types would increase in strength the more you killed them. This is all fine and dandy fighting normal enemies as the numbers were in expected ranges, so future fights would still be eclipsed by your own character’s growth. However, there are ones like werejackals that could summon weaker enemies in the tens and hundreds if you weren’t careful, leading to cases of encountering “super” jackals as a wilderness encounter later on that would tear you apart. This has been toned down for current releases now that it had kickstarted further development.
Another fun “gotcha” is killing a cat type, any cat at all. The first gives an indicator that this might have been a bad idea (message that its spirit yowls and disappears into the ground) but subsequent kills do not. What happens much, much further into the game is that there’s an invisible and powerful Cat Lord on a separate, guaranteed floor that must be traversed. He has a greater and greater chance of being hostile after the first cat death, with subsequent deaths further increasing its strength.
And let’s not forget the background corruption of certain deeper levels that you’re not aware of until you suddenly pop a Corruption message! Which also increases and without warning after a relatively long period of time. There is an in-game reason for this happening but it fails to let you know about it.