Mask of the Pact Bearer

Alter: This mask looks like a normal wooden mask before it's attuned to. When you attune to this mask, it changes to better represent your otherworldly patron's lingering presence over you. While you wear this mask, you can cast one spell from your patron's expanded spell list without expending a spell slot, if it is currently available to you. Once the mask has been used this way, it can't be used again until the next dawn.

Attunement: warlock
Rarity: Uncommon
Type: Mask
Cost: 190gp

Griffons Saddlebag, Vol 1