Mana Cairn

When enchanted land is tapped for mana, put
a charge counter on Mana Cairn.
Enchanted Land Gains:
"Remove X charge counters from Mana Cairn,
{t}: Add {g} for each charge counter removed this
way." and
"Rainbow: Remove 5 charge counters from Mana
Cairn,{t}: Put an Umbra counter on a permanent
you control." (As long as one mono-color permanent
of each color is in play, the game has Rainbow)
"The bones of this country burst with mana."