Mox Jet

This perfectly circular pendant is 2 inches across, and seems to be made from some sort of iron, always cold to the touch, and is decorated with tiny spikes and angles which look beautiful, but cut uncomfortably into your skin. The pendant opens to reveal a piece of jet, impossibly black and totally unblemished. As an action while holding the jet, you may cast any Warlock spell of 7th level or lower. You do not require material components of any kind to cast the spell. Spell attacks are made with a +10 bonus, and the spell save DC is 18. In addition, three times per long rest, you may use an action to gain the benefit of any Warlock Invocation. The effect of the Invocation lasts until the end of your next long rest.