Vile Requiem

At the beginning of your upkeep, you may put a verse counter on Vile Requiem.
{1}{B}, Sacrifice Vile Requiem: Destroy up to X target nonblack creatures, where X is the number of verse counters on Vile Requiem. They can't be regenerated.

The List

Commander 2013

At the beginning of your upkeep, you may put a verse counter on Vile Requiem.{1}{B}, Sacrifice Vile Requiem: Destroy up to X target nonblack creatures, where X is the number of verse counters on Vile Requiem. They can't be regenerated.

Urza's Saga

During your upkeep, you may put a verse counter on Vile Requiem.
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B, Sacrifice Vile Requiem: Destroy up to X target nonblack creatures, where X is the number of verse counters on Vile Requiem. Those creatures cannot be regenerated this turn.

Adding a counter is optional. If you forget to add one during your upkeep, you cannot back up and add one later.