Phantom Steed

If the exiled card has {X} in its mana cost, X is 0.

Although the token created by the triggered ability is attacking, it was never declared as an attacking creature (for the purposes of abilities that trigger whenever a creature attacks, for example).

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.

You declare which player or planeswalker the token is attacking as you put it onto the battlefield. It doesn't have to be the same player or planeswalker Phantom Steed is attacking.

If a token is exiled this way, it will cease to exist and won't return to the battlefield. Phantom Steed's last ability won't create any tokens.