Professor Onyx — ruling 1

For Professor Onyx's second loyalty ability, if an opponent has multiple creatures with the greatest power, that player choose which one to sacrifice. The next opponent in turn order chooses which creature they are sacrificing, then each other opponent in turn order does the same, knowing the choices made before them. Then all chosen creatures are sacrificed at the same time.

Professor Onyx — ruling 2

For Professor Onyx's last loyalty ability, "this process" is the following: First, the next opponent in turn order may choose a card in hand without revealing it, then each other opponent in turn order does the same. Then all the chosen cards are revealed and discarded at the same time and each opponent who didn't discard a card (whether they chose not to or had an empty hand) loses 3 life. This all will happen seven times, for a maximum loss of 21 life per opponent.

Professor Onyx — ruling 3

If Professor Onyx seems familiar, it's probably because you've seen this type of planeswalker before.

Professor Onyx — ruling 4

Each magecraft ability has a different effect, although they all have the same trigger condition, whenever you cast or copy an instant or sorcery spell.

Professor Onyx — ruling 5

For example, if you control Archmage Emeritus and cast an instant or sorcery spell, Archmage Emeritus's magecraft ability will trigger and you will draw a card.

Professor Onyx — ruling 6

If an effect creates a copy of an instant or sorcery spell, this will also cause the magecraft ability to trigger.

Professor Onyx — ruling 7

If an effect creates multiple copies of an instant or sorcery spell, magecraft abilities trigger once for each copy created by the effect.

Professor Onyx — ruling 8

Some effects instruct you to copy an instant or sorcery card in a zone other than the stack. These copies do not cause magecraft abilities to trigger. However, most effects that do this also allow you to cast the copy, and casting the copy will cause magecraft abilities to trigger.

Professor Onyx : règles, fonctionnement et interactions (MTG)

Professor Onyx 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

Magecraft — Whenever you cast or copy an instant or sorcery spell, each opponent loses 2 life and you gain 2 life. +1: You lose 1 life. Look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard. −3: Each opponent sacrifices a creature with the greatest power among creatures that player controls. −8: Each opponent may discard a card. If they don't, they lose 3 life. Repeat this process six more times.

Complete guide

Professor Onyx is a powerful Legendary Planeswalker that rewards players for mastering the arcane arts. With her signature Magecraft ability, she drains life from opponents every time you cast or copy a spell, making her a formidable win condition.

The Power of Magecraft

The defining feature of Professor Onyx is her Magecraft ability. This is a triggered ability that goes on the stack whenever you cast an instant or sorcery spell, or even when you create a copy of one. Unlike many effects that only trigger on casting, Magecraft allows you to scale your damage rapidly by using spells that copy other spells. Each time this happens, every opponent loses 2 life and you gain 2 life, providing a significant life swing.

Step-by-Step Resolution

When you activate Professor Onyx's abilities, follow these steps: For the +1 ability, you lose 1 life first, then look at your top three cards, picking one for your hand and binning the rest. For the -3 ability, opponents check their creatures for the highest power. If there is a tie, that opponent chooses one to sacrifice. For the -8 ultimate, opponents decide one by one whether to discard a card or lose 3 life. This specific choice and result repeats seven times in total, meaning an opponent could potentially lose 21 life if they have no cards to discard.

Common Pitfalls

A common mistake involves the -3 ability. Note that it does not target specific creatures; instead, it targets the opponents. This means creatures with Hexproof or Shroud are still vulnerable to being sacrificed if they have the highest power. Another nuance is with the Magecraft trigger: it only triggers for copies of spells on the stack. If an effect copies a card in a graveyard or exile but does not instruct you to 'cast' that copy, Magecraft will not trigger.

When to Play Her

Professor Onyx excels in control or combo-heavy decks that play many cheap instants and sorceries. She is best deployed when you can protect her for at least one turn to stabilize your life total with Magecraft or clear the board of a single large threat using her sacrifice ability. Her ultimate serves as a definitive finisher against opponents with low hand sizes.

Interaction examples

Sifting for Answers

You activate Professor Onyx's +1 ability. You lose 1 life, then look at the top three cards of your library. You find a land, a creature, and an instant. You put the instant into your hand to trigger Magecraft later and put the other two cards into your graveyard.

Handling Large Threats

Your opponent controls a 5/5 dragon and a 1/1 soldier. You activate Professor Onyx's -3 ability. Since the dragon has the greatest power (5), the opponent is forced to sacrifice it, regardless of protection like Indestructible.

The Final Drain

You activate the -8 ultimate. Your opponent has two cards in hand. For the first two repetitions, they choose to discard their cards to stay at their current life total. For the remaining five repetitions, they have no cards to discard and must lose 3 life each time, totaling 15 life lost.

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

How it works : Professor Onyx

Original English text — Wizards of the Coast / Scryfall

#1April 16, 2021· Wizards of the Coast
For Professor Onyx's second loyalty ability, if an opponent has multiple creatures with the greatest power, that player choose which one to sacrifice. The next opponent in turn order chooses which creature they are sacrificing, then each other opponent in turn order does the same, knowing the choices made before them. Then all chosen creatures are sacrificed at the same time.
No other card is named in this ruling.
#2April 16, 2021· Wizards of the Coast
For Professor Onyx's last loyalty ability, "this process" is the following: First, the next opponent in turn order may choose a card in hand without revealing it, then each other opponent in turn order does the same. Then all the chosen cards are revealed and discarded at the same time and each opponent who didn't discard a card (whether they chose not to or had an empty hand) loses 3 life. This all will happen seven times, for a maximum loss of 21 life per opponent.
No other card is named in this ruling.
#3April 16, 2021· Wizards of the Coast
If Professor Onyx seems familiar, it's probably because you've seen this type of planeswalker before.
No other card is named in this ruling.
#4April 16, 2021· Wizards of the Coast
Each magecraft ability has a different effect, although they all have the same trigger condition, whenever you cast or copy an instant or sorcery spell.
No other card is named in this ruling.
#5April 16, 2021· Wizards of the Coast
For example, if you control Archmage Emeritus and cast an instant or sorcery spell, Archmage Emeritus's magecraft ability will trigger and you will draw a card.
No other card is named in this ruling.
#6April 16, 2021· Wizards of the Coast
If an effect creates a copy of an instant or sorcery spell, this will also cause the magecraft ability to trigger.
No other card is named in this ruling.
#7April 16, 2021· Wizards of the Coast
If an effect creates multiple copies of an instant or sorcery spell, magecraft abilities trigger once for each copy created by the effect.
No other card is named in this ruling.
#8April 16, 2021· Wizards of the Coast
Some effects instruct you to copy an instant or sorcery card in a zone other than the stack. These copies do not cause magecraft abilities to trigger. However, most effects that do this also allow you to cast the copy, and casting the copy will cause magecraft abilities to trigger.
No other card is named in this ruling.