Barrensteppe Siege (Borderless) (TDM-384) - Tarkir: Dragonstorm: (enchantment) (Borderless)

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.