Ancient of liquid stone

Uncover 6 — When you play this from hand,
exile it with 6 depth counters on it, you may pay {2}
or tap a creature to remove a depth counter from it.
Cumulative upkeep — Destroy an artifact's with
the lowest converted mana cost. (At the beginning
of your upkeep, put an age counter on this
permanent, then sacrifice it unless you pay its upkeep
cost for each age counter on it.)