Windcrag Siege [Tarkir: Dragonstorm Promos]

As this enchantment enters, choose Mardu or Jeskai.

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

Jeskai At the beginning of your upkeep, create a 1/1 red Goblin creature token. It gains lifelink and haste until end of turn.