Mm'menon, the Right Hand 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

Flying You may look at the top card of your library any time. You may cast artifact spells from the top of your library. Artifacts you control have ": Add . Spend this mana only to cast a spell from anywhere other than your hand."

Complete guide

Meet Mm'menon, the Right Hand, a jellyfish advisor that turns your library into a secondary hand and your artifacts into specialized mana sources. This legendary creature offers incredible card advantage and the unique utility of 'future sight' for artifacts. Whether you are building around high-tech gadgets or deep-sea synergies, Mm'menon ensures your deck flows like the tide.

Eyes on the Horizon

Mm'menon grants you the ability to look at the top card of your library at any time, which does not use the stack. This knowledge is private to you, allowing you to plan your turns before you even draw. Furthermore, you may cast any artifact spells located there. This follows all normal timing rules; if it is an artifact creature, you can usually only cast it during your main phase while the stack is empty.

Conductive Trinkets

While Mm'menon is on the battlefield, every artifact you control gains a new activated ability: '{T}: Add {U}.' However, this blue mana comes with a specific restriction. You can only spend it to cast spells from zones other than your hand, such as the top of your library via Mm'menon’s own ability, your graveyard via other effects, or even from exile.

Timing and Restrictions

A common mistake is trying to use the artifact mana to pay for abilities or spells in your hand. Remember, the restriction applies to the act of casting a spell. If the top card of your library changes while you are in the middle of casting a spell (for example, if you cast a spell that allows you to draw as an additional cost), you cannot look at the new top card until you finish casting the current spell.

When to Deploy the Jellyfish

Mm'menon is best played when you have a board presence of non-mana-producing artifacts that can now be tapped for resources. Because it costs five mana, you want to ensure you have protection or an immediate artifact on top of your library to cast, ensuring you get value before your opponents can respond.

Interaction examples

Continuous Casting

With Mm'menon on the battlefield, you look at your top card and see an artifact. You tap an existing artifact you control for {U} using Mm'menon's granted ability. Since you are casting the artifact spell from your library (a zone other than your hand), the mana is spent legally. Once that spell is cast, you immediately look at the new top card to see if you can continue your chain.

Handling Non-Artifacts

If you look at the top card of your library and see a Sorcery, you cannot cast it using Mm'menon's ability. You must find a way to draw that card or move it (such as with a shuffle effect) to reveal an artifact underneath. You can, however, still tap your artifacts for blue mana to pay for that Sorcery if you manage to cast it from your graveyard or exile through other card effects.

Guide written with AI from the official text and rulings. Official English text prevails.