CardName: The Resurrection Ring
Cost: 3
Type: Legendary Artifact
Pow/Tgh: /
Rules Text: {B}, {T}: Return target creature card in your graveyard to
the battlefield. It gains haste. Exile it at the beginning
of the next endstep or if it would leave the battlefield.
Whenever a creature enters the battlefield from a graveyard,
target player with the most creatures in their graveyard
gains control of The Resurrection Ring.
Flavour Text:
Set/Rarity: Harry Potter and the Gathering of Magic Mythic
The Resurrection Ring
M
Legendary Artifact
, : Return target creature card in your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next endstep or if it would leave the battlefield.
Whenever a creature enters the battlefield from a graveyard, target player with the most creatures in their graveyard gains control of The Resurrection Ring.
Considering the phrasing for the Elder Wand, the second effect should probably trigger whenever a creature enters the battlefield from a graveyard.
I would suggest adding Whip of Erebos's clasue about leaving the battlefield, to prevent abuse.