Heron, Seer of a Psychic Age

When you cast this spell, you may unravel x
(to unravel, exile the top card of your deck).
For each card you unravel, this card costs {1}less.

{b}{b}, {t}: Tear away 5 (to tear away, exile 5 spells
from your graveyard).

Whenever you destroy or sacrifice a permanent,
unravel equal to its cost.