When the Invasion Tree reached the Underworld, it found only teeth and fury.

Kroxa and Kunoros

Vigilance, menace, lifelink
Whenever Kroxa and Kunoros enters or attacks, you may exile five cards from your graveyard. When you do, return target creature card from your graveyard to the battlefield.

March of the Machine Promos

March of the Machine

Vigilance, menace, lifelink
Whenever Kroxa and Kunoros enters the battlefield or attacks, you may exile five cards from your graveyard. When you do, return target creature card from your graveyard to the battlefield.

The last ability of Kroxa and Kunoros triggers and goes on the stack without a target. If you exile five cards from your graveyard, the second “reflexive” triggered ability will trigger. You’ll choose the target creature card for that second ability at that time.