Lantern Flare — ruling 1

If you're paying the cleave cost, you choose the value of X.

Lantern Flare — ruling 2

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.

Lantern Flare — ruling 3

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.

Lantern Flare — ruling 4

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.

Lantern Flare — ruling 5

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

Lantern Flare : règles, fonctionnement et interactions (MTG)

Lantern Flare is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Cleave (You may cast this spell for its cleave cost. If you do, remove the words in square brackets.) Lantern Flare deals X damage to target creature or planeswalker and you gain X life. [X is the number of creatures you control.]

How it works : Lantern Flare

Original English text — Wizards of the Coast / Scryfall

#1November 19, 2021· Wizards of the Coast
If you're paying the cleave cost, you choose the value of X.
No other card is named in this ruling.
#2November 19, 2021· Wizards of the Coast
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.
No other card is named in this ruling.
#3November 19, 2021· Wizards of the Coast
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.
No other card is named in this ruling.
#4November 19, 2021· Wizards of the Coast
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 , you can't cast it from your graveyard for its cleave cost.
No other card is named in this ruling.
#5November 19, 2021· Wizards of the Coast
If an effect allows you to “cast a spell without paying its mana cost,” you can't cast that spell for its cleave cost.
No other card is named in this ruling.