When Centaur Scrub enters the battlefield, return a land you control to its owner's hand.
: Add or to your mana pool.
Sacrifice Centaur Scrub: Add or to your mana pool.
When Centaur Scrub enters the battlefield, put a -1/-1 counter on target land.
: Add 
or 
to your mana pool. or to your mana pool.
