Sha'Kar, of the Burnwillows

Whenever a creature you control deals damage to
an opponent, add {r} or {g} to your mana pool.
Until end of turn, you don't lose this mana as
steps and phases end.
At the beginning of your end step, another target
player gains 1 life for each mana added to your
mana pool this turn by the effect of Sha'Kar, of
the Burnwillows.