Nightmare Shepherd
Enchantment Creature — Demon
Flying
Whenever another nontoken creature you control dies, you may exile it. If you do, create a token that's a copy of that creature, except it's 1/1 and it's a Nightmare in addition to its other types.
イラスト：
Theros Beyond Death Promos#108sレア英語適正
裁定
The token copies the creature as it last existed on the battlefield before it died, not as it existed in the graveyard before it was exiled.
The token copies exactly what was printed on the original creature and nothing else (unless that creature is copying something else; see below). It doesn’t copy whether that creature was tapped or untapped, whether it had any counters on it or Auras or Equipment attached to it, or any non-copy effects that had changed its power, toughness, types, color, or so on.
If the copied creature was copying something else, then the token enters the battlefield as whatever that creature copied.
If the copied creature had 
in its mana cost, X is considered to be 0.
Any enters-the-battlefield abilities of the copied creature will trigger when the token enters the battlefield. Any “as [this creature] enters the battlefield” or “[this creature] enters the battlefield with” abilities of the creature will also work.
If the token is a copy of a creature whose power and toughness are defined by an ability (usually printed as */* or similar), the token doesn’t copy the ability that defines its power and toughness. It remains a 1/1 creature.
If something becomes a copy of the token, the copy is also a 1/1 and a Nightmare.