Lockpicking is the skill used to open locked containers. This is primarily a rogue skill although any class can use it. Rogues have no maximum skill level that they can attain for this skill. There are many chests that can only be opened by rogues because they require a lockpicking skill of at least level three or more. Rangers can level their lockpicking skill to level two. All the other classes have this skill capped at level one, meaning that they cannot level the skill.
In addition to chests, the corpses of certain creatures require lockpicking to access the loot they carried. Skeletons and Bone Mages are locked approximately 50% of the time with a level 1 lock, meaning that anyone with Lockpicking level 1 can unlock it. Dracos are locked occasionally with a level 1 lock and occasionally with a level 2 lock. Dragons are occasionally locked with a level 2 lock and occasionally with a level 3 lock. Liches are occasionally locked with a level 3 lock.
If a corpse that is locked is on a tile, anything else on that tile is unavailable until the lock is picked. If a locked dragon falls on a character's corpse, that player's items become locked as well. If a skeleton dies on a zombie corpse, both the skeleton loot and the zombie loot will be hidden by the skeleton lock.