Petrichor, Elemental Sage

Whenever you draw one or more cards, exile
the top card of your library face down. At the beginning of your end step, if there are 10 or
more cards exile this way, shuffle them into
your library and take an extra turn after this
one.
You may reveal a card exiled with Petrichor
and cast it without paying its mana cost if it's
a creature card.