Hollowing Grounds

Hollowing Grounds enters the battlefield tapped
Whenever Hollowing Grounds untaps, put the top 5 cards of your library into your graveyard
{t}Add {1} to your mana pool
{t}Add {2} to your mana pool, use this mana only to cast or activate abilities of Hollow cards
{5}Return target Hollow card from your graveyard to your hand