(Centaur Grave isn't a spell.)
At the beginning of your end step, if you didn't cast any spells this turn, Centaur Grave deals 1 damage to you.
, : Scry 2.
: Add or to your mana pool.
Put Centaur Grave on top of your library: Add to your mana pool.
, 
: Scry 2.: Add 
or 
to your mana pool. to your mana pool. 
