Agridund, the Taxing

Bestow {g/w} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Agridund and creatures it enchants have cumulative upkeep {1}. (At the beginning of your upkeep, if this permanent is on the battlefield, put an age counter on this permanent. Then you may pay {1} for each age counter on it. If you don't, sacrifice it.)