Wildland Conduit

Wildland Conduit enters the battlefield with a -1/-1 counter.
Landfall — Whenever a land enters the battlefield under your control you may add or remove a -1/-1 counter from Wildland Conduit.
{t}: Add X mana in any combination of colors to your mana pool, where X equals the number of -1/-1 counters on Wildland Conduit. Spend this mana only to cast creature spells.