Aboroth

Creature - Elemental 9/9, 4GG (6)
Cumulative upkeep-Put a -1/-1 counter on Aboroth. (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.)¹
The Weatherlight banked sharply as the colossal beast rose up to crush the lone rider. "My bet's on the dirt, " Gerrard said flatly.
Illus. Brom

Gatherer Card Rulings [Nov 2009]

• 10/1/2008: Paying cumulative upkeep is always optional. If it's not paid, the permanent with cumulative upkeep is sacrificed. Partial payments of the total cumulative upkeep cost can't be made. For example, if a permanent with "cumulative upkeep {1}" has three age counters on it when its cumulative upkeep ability triggers, it gets another age counter and then its controller chooses to either pay {4} or sacrifice the permanent.

Format Legality	Legal in Vintage, Legacy Banned in Extended, Standard, MTGO Classic
Printings (1/6)	Weatherlight (Rare)