Seer Spriggan

Seer Spriggan enters the battlefield tapped.
As long as you control 10 or less other lands, Seer
Spriggan is a land. (It isn't a creature.)
As long as Seer Spriggan is a creature, whenever
an opponent activates a nonland mana ability,
you may put a land card from your hand or
graveyard onto the battlefield.
{t}: Add {c}{g}.