Maro's Gone Nuts

Name: Maro's Gone Nuts
Brand: Magic: The Gathering
Price: 0.27 USD

Double any effect that doubles. (It quadruples.)

Maro's Gone Nuts has 2 printings, first in Mystery Booster Playtest Cards 2019 (2019). It has 4 official rulings.

Legality

2019-11-12: Double strike isn’t an effect, so it’s not doubled.
2019-11-12: An effect “doubles” if it instructs a player to double something, or if it replaces an event with “double that much,” “twice as many,” or similar.
2019-11-12: An effect that increases something by a specific amount (such as the first ability of Jaya, Venerated Firemage) isn’t doubling, even if the result is double the normal result.
2019-11-12: If two Maro’s Gone Nuts are on the battlefield, effects that double instead octuple. If three are on the battlefield, effects that double instead sexdecuple, and so on.