Ravenloft: Ghosthunter, a magic quarterstaff for D&D 5th Edition

Ghosthunter
Magic weapon (quarterstaff), very rare (requires attunement)

You gain a +2 bonus to attack and damage rolls with this magic weapon.

In addition, you may hit and damage creatures on the Border Etheral.

Finally, you have advantage on Charisma and Wisdom saving throws against undead.

Naru Nopteko was a shaman who devoted his life to combating the restless dead on the Demiplane of Dread and Desire.  The Dark Powers knew Naru too well and finally broke the old man, but not before he hid his staff away from their prying eyes, his parting gift to those willing to stand tall against the darkness.