Hundred-Year Curse

Hundred-Year Curse enters the battlefield with
100 time counters on it. At the beginning of each
end step or whenever a player casts a spell or
draws a card, remove a time counter from it.
During each player's untap step, that player may
only untap half of their tapped permanents,
rounded down.
Whenever a player casts a spell, that player draws
a card.