The phyrexian Deserts

The phyrexian Deserts enters the battlefield tapped unless a creature on the battlefield has a -1/-1 counter on it.
{t}, pay 1 life: add{b}
{t}, {1}: put a -1/-1 counter onto target creature
At the beginning of your end step, if no creature has a -1/-1 counter on it, sacrifice The phyrexian Deserts.