Precipice of the Fallen

Precipice of the Fallen comes into play tapped.
{t} Precipice of the Fallen gives {x} mana, in which {x} is the amount of Dragons and Wyverns in your graveyard. This can only be played once each time a Dragon or Wyvern is placed into your graveyard.
{t} Exile a Wyvern or Dragon card from your graveyard, search your deck for a Mountain and
play it.