Inelul Magilor Nebuni (5e Equipment)
From D&D Wiki
Ring, legendary (requires attunement)
An intricate silver ring with a black diamond at its center which seems to absorb and distort the light around it.
Visage of the Lost Upon inspecting the ring, the diamond will show the image of a deceased loved one alongside a their voice whispering to them, just barely inaudible. The holder of the ring must make a DC 18 Wisdom saving throw or be forced to wear the ring. Upon wearing the ring, it cannot be removed outside the use of a Wish spell.
Host of Power The wearer gains the spellcasting feature as well as spell slots for a 12th level full caster. You learn 1d4+8 Warlock spells and Charisma is your spellcasting ability for these spells and you regain all spell slots at the end of a long rest.
Clutch of Insanity At dawn, the wearer must make a DC 18 Wisdom saving throw or roll off the long-term madness table. When casting a spell of third level or higher, the wearer must make a DC 16 Wisdom saving throw or roll off the short-term madness table. If they fail the saving throw by more than five, roll off the indefinite madness table instead.