Barrensteppe Siege (171) [Tarkir: Dragonstorm Promos]

As this enchantment enters, choose Abzan or Mardu. • Abzan — At the beginning of your end step, put a +1/+1 counter on each creature you control. • Mardu — At the beginning of your end step, if a creature died under your control this turn, each opponent sacrifices a creature of their choice.