Necklace of Immortality

Equipped creature has hexproof and whenever equipped creature deals combat damage to player, shuffle target player's graveyard into their library.
Whenever a nontoken creature enters the battlefield under your control, attach Necklace of Immortality to it.
When Necklace of Immortality is put into your graveyard from anywhere, shuffle Necklace of Immortality and your graveyard into your library.