Heart of Bogardan
Cumulative upkeep is almost always a downside mechanic, the slow-leak tax that pulls cards like Glacial Chasm off the table once the payments get too steep. Here the designers inverted it: the escalating cost is not a punishment to outlast but a timer you wind up on purpose. Each upkeep you pay, another age counter lands, and the payload waiting at the end scales with the count, twice the counters minus two, dealt to a player and every creature they control the moment the payments stop. The structural twist is that you were never going to pay forever, so the only real decision the card asks is when to let it die. It is built to be lethal precisely because you let the upkeep lapse on your own terms, converting a mechanic meant to bleed you into a fuse you light deliberately. The cost ramp is what keeps the rate fair: getting the damage high enough to sweep a board means several turns of mounting payments with nothing on the table to show for them, an enchantment that accrues debt and does nothing else while you wait for the window. Board wipe and finisher folded into one permanent, where the entire skill expression is the timing of its own sacrifice.
Rules text
(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 this enchantment's cumulative upkeep, this enchantment deals X damage to target player or planeswalker and each creature that player or that planeswalker's controller controls, where X is twice the number of age counters on this enchantment minus 2.