Tuskeri Firewalker

A boast ability can be activated at any point after the creature with that ability has been declared as an attacker. This can be before blockers are declared, after blockers are declared but before combat damage is dealt, during combat after combat damage is dealt, during the postcombat main phase, during the end step, or, in some unusual cases, during the cleanup step.

If you don't play the card by the end of the turn, it will remain exiled. Boasting again on a future turn won't let you play that card.

The card you exile with the boast ability is exiled face up.

If an effect adds additional combat phases to a turn and a creature with a boast ability attacks more than once during that turn, its boast ability can still be activated only once.