Big Rock Candy Mountain

{t} Add {r} to your mana pool.
Tap an untapped human you control: Add
1 Exploration counter to Big Rock Candy
Mountain.
When Big Rock Candy Mountain has 5 or more
Exploration counters on it, it has {t} add {g},
{w}, {u} or {r} to your mana pool, and "human
creatures you control have Hexproof."