Pyrohemia

At the beginning of the end step, if no creatures are on the battlefield, sacrifice this enchantment.
{R}: This enchantment deals 1 damage to each creature and each player.

The List

Commander Anthology

At the beginning of the end step, if no creatures are on the battlefield, sacrifice Pyrohemia.
{R}: Pyrohemia deals 1 damage to each creature and each player.

Commander 2011

Planar Chaos

At end of turn, if no creatures are in play, sacrifice Pyrohemia.
{R}: Pyrohemia deals 1 damage to each creature and each player.

Each activation is considered a new damage effect. An activation can only be 1 point of damage.

It will stay on the battlefield if there is a creature that is put into the graveyard during the end step. This is because this ability will not trigger at all if there is at least one creature on the battlefield as the end step begins.

Note that "until end of turn" effects wear off after "at the beginning of the end step" triggered abilities, so an artifact that animates until end of turn can keep this on the battlefield.