cumulative upkeep 2 (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.)
when a player doesn't pay heart of bogardan's cumulative upkeep, heart of bogardan deals x damage to target player and each creature he or she controls, where x is twice the number of age counters on heart of bogardan minus 2.