As Molten Echoes enters, choose a creature type. Whenever a nontoken creature you control of the chosen type enters, create a token that's a copy of that creature. That token gains haste. Exile it at the beginning of the next end step.
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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 copied creature will also work.
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If the copied creature has {X} in its mana cost, X is 0.
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If the copied creature is copying something else, the token enters the battlefield as whatever that creature is copying.
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If the nontoken creature leaves the battlefield before Molten Echoes's triggered ability resolves, the token that's created uses the creature's last known information from before it left.
2020-04-17
The token copies exactly what is printed on the creature and nothing else (unless that creature is copying something else; see below). It doesn't copy whether that creature is tapped or untapped, whether it has any counters on it or Auras and/or Equipment attached to it, or any non-copy effects that changed its power, toughness, types, color, and so on.
2020-04-17
You must choose an existing creature type, such as Human or Warrior. Card types such as artifact and supertypes such as legendary can't be chosen.