Eye of the Abyss

Wondrous item, artifact (requires attunement)

A jagged, multifaceted crystal roughly the size of a fist, the Eye of the Abyss seems to consume light rather than reflect it. Deep within its core, a swirling vortex of impossible colors twists continuously, whispering promises of forbidden knowledge.

Properties

While attuned to the Eye, you gain the following benefits:

• Void Sight: You have truesight out to a range of 120 feet. You can see into the Ethereal Plane and the Void within that range.
• Abyssal Secrets: You have advantage on Intelligence (Arcana) and Intelligence (Religion) checks related to the Void and abberations.

Curse of the Void

Whenever you use the Eye to cast a spell or gaze deeply into the Void, you must make a DC 18 Wisdom saving throw. On a failed save, you take 4d10 psychic damage and suffer a short-term madness effect. If you fail the saving throw by 5 or more, you instead suffer a long-term madness effect.