mana-lock seeker

when this creature enters the battlefield put an unlocked counter on a tap ability on a land.
a land ability with an unlocked counter loses
its old effects and becomes "{t}: add x mana to
your mana pool."
x is equal to the total number of mana symbols
in the ability (so {t}: add {u} or {r} mana to your
mana pool" becomes "{t}: add {u}{r} to your mana
pool").