Sundial of Sursi

At the beginning of each end step, if you gained
life this turn, untap Sundial of Sursi and put a
charge counter on it.
{w}, {t}, Put a charge counter on Sundial of Sursi:
You gain an amount of life equal to the number
of charge counters on it.
{ut}, Remove four charge counters from Sundial of
Sursi: Search your library for a white card with
converted mana cost equal to the amount of life
you gained this turn, exile it, then shuffle your
library. You may play cards exiled this way.