Nemesis Trap — ruling 1

If you cast Nemesis Trap for {B}{B}, you may still target any attacking creature, not just the white attacking creature.

Nemesis Trap — ruling 2

An "attacking creature" is one that has been declared as an attacker this combat, or one that was put onto the battlefield attacking this combat. Unless that creature leaves combat, it continues to be an attacking creature through the end of combat step, even if the player it was attacking has left the game, or the planeswalker it was attacking has left combat.

Nemesis Trap — ruling 3

If you cast Nemesis Trap during your opponent's declare attackers step, you'll put the token onto the battlefield before the declare blockers step begins and you can block with it this combat. If you cast Nemesis Trap later in the combat phase a, you won't be able to block with the token.

Nemesis Trap — ruling 4

The token you put onto the battlefield copies exactly what was printed on the exiled creature and nothing more (unless it was copying something else or it was a token; see below). It doesn't copy whether the exiled creature was tapped or untapped, whether it had any counters on it or Auras attached to it, or any non-copy effects that changed its power, toughness, types, color, or so on. For example, if Nemesis Trap targets an animated Celestial Colonnade, the token you put onto the battlefield will be a Celestial Colonnade that's just a land. (Because of this, Nemesis Trap has received minor errata to specify that you put a token, not a "creature token," onto the battlefield.)

Nemesis Trap — ruling 5

If the exiled creature was copying something else (for example, if it was a Jwari Shapeshifter), then your token enters as a copy of whatever the exiled creature was copying.

Nemesis Trap — ruling 6

If the exiled creature was a token, your token copies the original characteristics of that token as stated by the effect that put it onto the battlefield.

Nemesis Trap — ruling 7

If the exiled creature has {X} in its mana cost (such as Protean Hydra), X is considered to be zero.

Nemesis Trap — ruling 8

Any "enters" abilities of the exiled creature will trigger when the token is put onto the battlefield. Any "as [this creature] enters" or "[this creature] enters with" abilities of the chosen creature will also work.

Nemesis Trap : règles, fonctionnement et interactions (MTG)

Nemesis Trap is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

If a white creature is attacking, you may pay rather than pay this spell's mana cost. Exile target attacking creature. Create a token that's a copy of that creature. Exile it at the beginning of the next end step.

How it works : Nemesis Trap

Original English text — Wizards of the Coast / Scryfall

#1March 1, 2010· Wizards of the Coast
If you cast Nemesis Trap for , you may still target any attacking creature, not just the white attacking creature.
No other card is named in this ruling.
#2March 1, 2010· Wizards of the Coast
An "attacking creature" is one that has been declared as an attacker this combat, or one that was put onto the battlefield attacking this combat. Unless that creature leaves combat, it continues to be an attacking creature through the end of combat step, even if the player it was attacking has left the game, or the planeswalker it was attacking has left combat.
No other card is named in this ruling.
#3March 1, 2010· Wizards of the Coast
If you cast Nemesis Trap during your opponent's declare attackers step, you'll put the token onto the battlefield before the declare blockers step begins and you can block with it this combat. If you cast Nemesis Trap later in the combat phase a, you won't be able to block with the token.
No other card is named in this ruling.
#4March 1, 2010· Wizards of the Coast
The token you put onto the battlefield copies exactly what was printed on the exiled creature and nothing more (unless it was copying something else or it was a token; see below). It doesn't copy whether the exiled creature was tapped or untapped, whether it had any counters on it or Auras attached to it, or any non-copy effects that changed its power, toughness, types, color, or so on. For example, if Nemesis Trap targets an animated Celestial Colonnade, the token you put onto the battlefield will be a Celestial Colonnade that's just a land. (Because of this, Nemesis Trap has received minor errata to specify that you put a token, not a "creature token," onto the battlefield.)
Card named in this ruling
Copy
#5March 1, 2010· Wizards of the Coast
If the exiled creature was copying something else (for example, if it was a Jwari Shapeshifter), then your token enters as a copy of whatever the exiled creature was copying.
Card named in this ruling
Copy
#6March 1, 2010· Wizards of the Coast
If the exiled creature was a token, your token copies the original characteristics of that token as stated by the effect that put it onto the battlefield.
No other card is named in this ruling.
#7March 1, 2010· Wizards of the Coast
If the exiled creature has in its mana cost (such as Protean Hydra), X is considered to be zero.
No other card is named in this ruling.
#8March 1, 2010· Wizards of the Coast
Any "enters" abilities of the exiled creature will trigger when the token is put onto the battlefield. Any "as [this creature] enters" or "[this creature] enters with" abilities of the chosen creature will also work.
No other card is named in this ruling.
#9March 1, 2010· Wizards of the Coast
If the targeted creature is an illegal target by the time Nemesis Trap resolves, the entire spell doesn't resolve. You won't get a token.
No other card is named in this ruling.