Rellias, Cultivating Vitalist

When Rellias, Cultivating Vitalist enters the battlefield, add X mana in any combination of
colors to your mana pool, where X is the number
of elves you control.
Mana doesn't empty from your mana pool as
steps and phases end.
{4}{w}, {t}: Gain X life where X is the amount of
mana in your mana pool.