Path of Peril
Sorcery
Cleave 
Destroy all creatures [with mana value 2 or less].
To Olivia's guests, a welcome. To everyone else, a warning.
Kasia 'Kafis' Zielińska
Innistrad: Crimson Vow (VOW)
• #124Rulings
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.
(wotc • 2021-11-19)
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.
(wotc • 2021-11-19)
You can't cast a spell for both its cleave cost and another alternative cost. For example, if an effect gives an Alchemist's Retrieval in your graveyard a flashback cost of {U}, you can't cast it from your graveyard for its cleave cost.
(wotc • 2021-11-19)
If an effect allows you to “cast a spell without paying its mana cost,” you can't cast that spell for its cleave cost.
(wotc • 2021-11-19)
Rulings
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.
(wotc • 2021-11-19)
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.
(wotc • 2021-11-19)
You can't cast a spell for both its cleave cost and another alternative cost. For example, if an effect gives an Alchemist's Retrieval in your graveyard a flashback cost of {U}, you can't cast it from your graveyard for its cleave cost.
(wotc • 2021-11-19)
If an effect allows you to “cast a spell without paying its mana cost,” you can't cast that spell for its cleave cost.
(wotc • 2021-11-19)