Fierce Retribution

If an effect allows you to “cast a spell without paying its mana cost,” you can't cast that spell for its cleave cost.

If you cast a spell for its cleave cost, that spell doesn't have any of the text in square brackets while it's on the stack.

A cleave cost is an alternative cost that's paid instead of the spell's mana cost. Casting a spell for its cleave cost doesn't change the spell's mana value.