Gravekeeper's Shaman gains +0/+X, where X is equal to the number of Gravekeepers in your graveyard.

When a creature's ability is activated in the graveyard, or an opponent would cast a creature from their graveyard, counter that spell or ability unless that spell is a Gravekeeper or that ability is from a Gravekeeper card.

Necrovalley gains indestructible while it and Gravekeeper's Shaman are on the battlefield under your control, also your opponent's enchantments cost {3} more to cast.