Dominaria Spoiler Digest - Who's Who and What's What from the Release Notes
Nacatl War-Pride must be blocked by exactly one creature if able.
Whenever Nacatl War-Pride attacks, create X tokens that are copies of Nacatl War-Pride and that are tapped and attacking, where X is the number of creatures defending player controls. Exile the tokens at the beginning of the next end step.
5/1/2007 If it’s impossible for Nacatl War-Pride to be blocked by exactly one creature, then the defending player may block it with multiple creatures or may leave it unblocked.
5/1/2007 If Nacatl War-Pride has left the battlefield by the time the triggered ability resolves, the tokens will still enter the battlefield as copies of Nacatl War-Pride.
5/1/2007 If Nacatl War-Pride becomes a copy of something else after the ability triggers but before it resolves, the tokens will enter the battlefield as copies of whatever the ex-Nacatl War-Pride is now. If Nacatl War-Pride became a copy of something else and then left the battlefield, the tokens will enter the battlefield as copies of whatever it was copying when it last existed on the battlefield.
5/1/2007 The tokens enter the battlefield attacking, even if the attack couldn’t legally be declared.
5/1/2007 Putting an attacking creature onto the battlefield doesn’t trigger “When this creature attacks” abilities. It also won’t check attacking restrictions, costs, or requirements.
5/1/2007 In a multiplayer game in which you’re allowed to attack only one player each combat, the new creatures will be attacking the same player as Nacatl War-Pride. In a multiplayer game in which you may attack multiple players, you choose the player each new creature is attacking. It must be a player you’re allowed to attack.