Vrukaal's Vernal Chant

Add X colorless mana to your mana pool, where
X is the number of land cards in your graveyard.
Until end of turn, this mana doesn't empty from
your mana pool as phases begin and end.
Retrace (You may cast this card from your
graveyard by discarding a land card in addition to
paying its other costs.)
"The swamp holds many forgotten memories."