Ritual of blood

As an additional cost to ritual of blood, sacrifice a creature
Cumulative upkeep - each opponent looses 1 life and you gain 1 life (at the beginning of your upkeep, put an age counter on this permenant, then sacrifice it unless you pay it's upkeep cost for each age counter on it.)
The ritual of blood was a long-forgotten ritual once practiced by the ancient vampires, but rituals like this don't stay forgotten forever ...