Amulet of the Forgotten Prince

A Strange amulet of a doorway with the symbol of Orcus on the back.  Once per day you can use the power of the prince to summon 1 or more demons to aid you for 60 seconds.  The combined challenge rating of the demons cannot exceed your warlock level.  Once summoned, the demons will follow your commands to the best of their ability for 1 minute.  After the minute has expired the demons disappear into a pile of ash and smoke.