The Keys of Sirdan, a lejendary Thief, consist of 39 keys held
together by a mithral ring. No keys can be removed from or added to
the ring. There is a base 20% chance that for any key lock a character
encounters, the key to the lock can be found on the ring. Every point
of Intelligence and Wisdom possessed by a character adds 1% to the
base chance. The item is usable by all classes, but Thieves receive an
additional bonus of 20% per chance, and Assassins receive an
additional bonus of 10% per chance (plus the 20% for a Thief). It
takes one melee round to check the ring, and only one attempt may
be made for each lock encountered.