Gift of Doom
Enchantment — Aura
Enchant creature
Enchanted creature has deathtouch and indestructible.
Morph—Sacrifice another creature. (You may cast this card face down as a 2/2 creature for 
. Turn it face up any time for its morph cost.)
As this Aura is turned face up, you may attach it to a creature.
James Zapata
Commander 2019 (C19)
• #17Rulings
This doesn't target the creature Gift of Doom will enchant, so an opponent's creature with hexproof or a creature with shroud may be chosen this way. The chosen recipient must be able to legally be enchanted by the Aura, so a creature with protection from black can't be chosen this way.
(wotc • 2019-08-23)
If there's no creature you can legally attach Gift of Doom to as you turn it face up, or if you choose not to attach it to a creature, it's put into its owner's graveyard.
(wotc • 2019-08-23)
You can't pay Gift of Doom's morph cost more than once.
(wotc • 2019-08-23)
No player may take any actions between the time you announce that you're turning Gift of Doom face up and the time it's attached to the chosen creature.
(wotc • 2019-08-23)
Rulings
This doesn't target the creature Gift of Doom will enchant, so an opponent's creature with hexproof or a creature with shroud may be chosen this way. The chosen recipient must be able to legally be enchanted by the Aura, so a creature with protection from black can't be chosen this way.
(wotc • 2019-08-23)
If there's no creature you can legally attach Gift of Doom to as you turn it face up, or if you choose not to attach it to a creature, it's put into its owner's graveyard.
(wotc • 2019-08-23)
You can't pay Gift of Doom's morph cost more than once.
(wotc • 2019-08-23)
No player may take any actions between the time you announce that you're turning Gift of Doom face up and the time it's attached to the chosen creature.
(wotc • 2019-08-23)