Chests are not always harmless. Apart from the threat of mimics, normal treasure chests are often trapped by their owners in order to prevent any tampering with them due to potentially lethal consequences. However, the adventurer isn't completely helpless against these traps. With the detect trap spell, it is possible to find these hidden dangers. The unlock spell further opens these chests, while at the same time destroying the traps.
There are four different traps found in chests:
Poison
From the harmful traps, this is still the least damaging one. Opening the chest, the thief is greeted with a spray of poison. Nothing that a cure spell can't fix.
Acid
This trap is more nasty than the poison-trap. Instead of poison, the thief is sprayed with acid. The acid is very damaging, and if not properly treated with the heal spell, has potential lasting health-effects.
Bomb
This is the worst of all traps. Trying to open the chest will trigger a bomb-trap which will blow apart the chest, destroying its contents. The powerful explosion will seriously injure anyone nearby, meaning the entire party.
The only trap which can also be encountered hiding in the floor of dungeons (especially Ultima V).
Curse
This is the only trap that does not do any physical harm. Instead, it puts the curse spell on the person fiddling with the lock. Seen only on the Serpent Isle, these traps were rarely encountered.