The Goddess' Shriek

Reveal the Goddess' Shriek from your hand:
Choose one: The Goddess' Shriek becomes a copy
of target instant or sorcery except it has a mana
cost of X and it keeps all its original abilities. The
number of echo counters on it becomes that
spell's mana cost; or pay {u}, if you do, remove an
echo counter from it.
X must be equal to the number of echo counters.