Valley of Lost Giants

Creatures with power 4 or greater can't attack or block and don't untap during their controllers' untap steps for as long as you control Valley of Lost Giants.
{t}: Add {c}
Cumulative upkeep - Pay 1 life (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.)