Stone guardians are immune to weapons and fire. They are inanimate, so gases do not affect them, and they reflect spells back at you. They have a huge amount of HP, so it is not practical to kill them with offensive staves, even if you can survive the bolts that get reflected. You may not need to kill stone guardians, as they can be avoided, and their attacks are not so powerful that you cannot afford to take a hit in order to get past. If you must kill one, the easiest way is to either negate the guardian, which will kill it instantly, or to throw a potion of descent at it. Falling will always kill stone guardians due to a special case in the game code; this prevents them from blocking the path through the level below.
| The charming inhabitants of the dungeon: