Armageddon Clock (SUM-234) - Summer Magic / Edgar

At the beginning of your upkeep, put a doom counter on Armageddon Clock.
At the beginning of your draw step, Armageddon Clock deals damage equal to the number of doom counters on it to each player.
: Remove a doom counter from Armageddon Clock. Any player may activate this ability but only during any upkeep step.