Scarlet Spider, Kaine — ruling 1

Mayhem represents an alternative cost that can be paid to cast a spell from your graveyard if you discarded the card with mayhem that turn. You must pay any additional costs the spell has.

Scarlet Spider, Kaine — ruling 2

You must follow all normal timing rules when casting a spell with mayhem. For example, you can't cast a creature card with mayhem you couldn't normally cast during an opponent's turn, even if you discard that card during an opponent's turn.

Scarlet Spider, Kaine : règles, fonctionnement et interactions (MTG)

Scarlet Spider, Kaine 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

Menace (This creature can't be blocked except by two or more creatures.) When Scarlet Spider enters, you may discard a card. If you do, put a +1/+1 counter on him. Mayhem (You may cast this card from your graveyard for if you discarded it this turn. Timing rules still apply.)

How it works : Scarlet Spider, Kaine

Original English text — Wizards of the Coast / Scryfall

#1September 19, 2025· Wizards of the Coast
Mayhem represents an alternative cost that can be paid to cast a spell from your graveyard if you discarded the card with mayhem that turn. You must pay any additional costs the spell has.
No other card is named in this ruling.
#2September 19, 2025· Wizards of the Coast
You must follow all normal timing rules when casting a spell with mayhem. For example, you can't cast a creature card with mayhem you couldn't normally cast during an opponent's turn, even if you discard that card during an opponent's turn.
No other card is named in this ruling.