Vortex of the Void

As an additional cost to cast Vortex of the Void,
pay three times X life. Vortex of the Void enters
the battlefield with X death counters on it.
At the beginning of your end step, each opponent
loses life equal to the number of death counters
on Vortex of the Void. You gain life equal to the
life lost this way.
(For example, if you pay {3}{w}{b} to cast Vortex of the
Void, you pay 3 life, and X equals 1.)