Skull keys are a more advanced form of lockpicks. While the common lockpick can only open normal locks, skull keys can also open magically locked crates and doors. They are therefore extremely useful when such a lock has to be opened and the area doesn't allow the casting of the spell Unlock Magic.
Unfortunately, a skull key is only good for a single lock. Nonetheless, these are a must have for every adventurer, because with them even non-magic users can open magic locks.
These peculiar keys were recently invented by Shenstone, a skilled smith of Minoc. By a little-known principle of magical absorption, a skull key can reliably open any magically locked door, although it will become a useless piece of steel after one use.