Risen Slime

This land enter the battlefield with 3 counters
on it. At the beginning of your upkeep remove
a counter on it. When it no longer have any
counter, unleashed this land.
{t}:Add {u}. If this land is unleashed, add {b} too.
The change happened whilst I slept. When at last I
awaked, it was to discover myself sucked into a slimy
expanse of hellish black mire which extended about
me in monotonous undulations as far as I could see.
Dagon—H. P. Lovecraft