They don't like arrows fired from stealth either.
It helps to just sneak up and smack any corpse that looks suspicious. You'll start to learn the warning signs. Also, move slowly through tombs so you can pick them off in smaller numbers. Move to fast and you'll get stuck in a whole room of them crawling out of the walls. . . .
Yeah. I was outside when I saw something like altar. When I approached it, the draughts spotted me even I went stealth. They surprised me.
In tombs, I moved slowly and tried to take down one by one.
Thanks all for advises. I do have fire spell, but haven't used it much.