If a creature attacking causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

First strike

Whenever a Samurai or Warrior you control attacks alone, untap it. If it's the first combat phase of the turn, there is an additional combat phase after this phase.

Haste

Whenever Risona, Asari Commander deals combat damage to a player, if it doesn't have an indestructible counter on it, put an indestructible counter on it.

Whenever combat damage is dealt to you, remove an indestructible counter from Risona.

Flash

As long as The Wandering Emperor entered the battlefield this turn, you may activate her loyalty abilities any time you could cast an instant.

+1: Put a +1/+1 counter on up to one target creature. It gains first strike until end of turn.

-1: Create a 2/2 white Samurai creature token with vigilance.

-2: Exile target tapped creature. You gain 2 life.