Dark Shard Amulet

Wondrous item, amulet

This amulet is fashioned from a single shard of resilient extra-planar material.
While you are wearing it, you gain the follow benefits:

• You can use the amulet as a spell casting focus for your warlock spells.
• You can try to cast a cantrip that you don't know. The cantrip must be on the warlock spell list, and you must make a DC 10 Intelligence (Arcana) check.
  If this check succeeds, you can cast the spell. If the check fails, so does the spell, and the action used to cast the spell is wasted.
  In either case, you can't use this property again until you finish a long rest.