In MTG, affinity for artifacts means a spell costs {1} less to cast for each artifact you control (rule 702.41a of the Comprehensive Rules). It only ever removes generic mana, never coloured mana, and it never changes the spell's mana value. With four artifacts under your control, Frogmite costs nothing. Mana Grove, a free MTG deck builder for Commander, publishes this guide to affinity for artifacts and checks every card in it against its own card database.
This guide is part of our MTG keywords and mechanics glossary, the index of every mechanic guide on Mana Grove.
What does affinity for artifacts mean?
Affinity is a keyword with two short lines in the rules:
Rule 702.41a
Affinity is a static ability that functions while the spell with affinity is on the stack. "Affinity for [text]" means "This spell costs {1} less to cast for each [text] you control."
Rule 702.41b
If a spell has multiple instances of affinity, each of them applies.
Three things follow. Affinity works on the stack, so it applies however the spell is cast. It counts what you control on the battlefield: rule 109.2 reads a card type in rules text as a permanent of that type, so artifacts in your hand or graveyard don't count, and neither does the affinity spell itself, which is still on the stack. And every artifact counts: artifact creatures, Equipment, artifact lands, and tokens such as Treasure (111.10a).
How much does an affinity spell cost?
Start from the printed cost, add any extra costs, then take off {1} for each artifact. Rule 601.2f sets that order, and the mana part "can't be reduced to less than {0}."
| Spell | Printed cost | Artifacts you control | You pay |
|---|---|---|---|
| Frogmite | {4} | 2 | {2} |
| Frogmite | {4} | 4 or more | {0} |
| Myr Enforcer | {7} | 5 | {2} |
| Thoughtcast | {4}{U} | 6 | {U} |
Artifacts past the generic part are wasted: six artifacts take Thoughtcast down to {U} and no further.
When are your artifacts counted?
Once, as you cast the spell. The reduction is applied when you work out the total cost, which then becomes "locked in" (601.2f), and only after that do you activate mana abilities (601.2g) and pay (601.2h). So a Treasure counts toward the reduction and can then be sacrificed for the mana you still owe, and losing an artifact after the cost is locked doesn't make the spell more expensive.
Does affinity reduce coloured mana?
No. Rule 118.7a: effects that reduce a cost by generic mana "affect only the generic mana component of that cost." Affinity never takes Thoughtcast below {U}, or Urza, Chief Artificer below {W}{U}{B}. Only a spell whose mana cost is all generic, like Frogmite or Myr Enforcer, can become free through affinity alone.
Does affinity change a spell's mana value?
No. Mana value is the total mana in the card's mana cost (202.3), and affinity changes only what you pay. A Myr Enforcer cast for {0} still has a mana value of 7, which matters for anything that reads mana value, from counterspells that check it to cascade.
What else can a spell have affinity for?
Whatever the card names after "for", usually a card type or a subtype. Each one counts exactly what it names, among the permanents you control.
| Card | Cost | Affinity for | What it is |
|---|---|---|---|
| Razor Golem | {6} | Plains | A 3/4 artifact creature with vigilance |
| Tomik, Wielder of Law | {1}{W}{B} | planeswalkers | A 2/4 flier with vigilance; an opponent who attacks you or your planeswalkers with two or more creatures loses 3 life and you draw a card |
| Nahiri, Forged in Fury | {4}{R}{W} | Equipment | A 5/4 that exiles your top card, playable this turn, whenever an equipped creature you control attacks |
| Urza, Chief Artificer | {3}{W}{U}{B} | artifact creatures | A 4/5 that gives your artifact creatures menace and makes a Construct token at each of your end steps |
Affinity for Plains counts every land with the Plains type, basic or not. Razor Golem has a colourless identity, so any Commander deck may run it, but lands with the Plains type only go in decks whose commander has white in its colour identity (903.5d), so in practice it only gets cheap there. Urza counts artifact creatures only, so a Treasure does nothing for him.
Which affinity cards should you know?
The classic ones cost little or nothing once the battlefield fills up with artifacts.
| Card | Cost | What it is | How it plays |
|---|---|---|---|
| Frogmite | {4} | 2/2 artifact creature | Free with four artifacts out |
| Myr Enforcer | {7} | 4/4 artifact creature | Free with seven, and a cheap 4/4 well before that |
| Thoughtcast | {4}{U} | Sorcery | Draw two cards, for {U} with four artifacts |
| Thought Monitor | {6}{U} | 2/2 flying artifact creature | Draws two cards when it enters, for {U} with six artifacts |
| Mycosynth Golem | {11} | 4/5 artifact creature | Gives your artifact creature spells affinity for artifacts too |
| Emry, Lurker of the Loch | {2}{U} | 1/2 legendary creature | Mills four, then taps to let you cast an artifact card from your graveyard this turn |
How does affinity work in Commander?
Two things change. Rule 903.8 adds {2} of commander tax for each previous cast from the command zone, and since increases come before reductions (601.2f), affinity takes the tax off too: Emry cast a second time with four artifacts out costs {U}. And the commanders that carry affinity lead decks built around what they count: Emry wants artifacts, Urza wants artifact creatures, Nahiri wants Equipment. The Commander hub has more commanders to build around.
Frequently asked questions
What does affinity do in MTG?
Affinity for artifacts makes a spell cost {1} less to cast for each artifact you control (Comprehensive Rules 702.41a). It only ever removes generic mana, never coloured mana, and it never changes the spell's mana value, so with four artifacts under your control Frogmite costs nothing.
Does affinity stack?
Yes. Rule 702.41b says that if a spell has more than one instance of affinity, each of them applies. With Mycosynth Golem on the battlefield, Frogmite has affinity for artifacts twice, so each artifact takes {2} off, and the Golem plus one other artifact make Frogmite free.
Do Treasure tokens and artifact lands count for affinity?
Yes. A Treasure is a colourless artifact token (111.10a) and an artifact land is an artifact as well as a land, so both count. You can count a Treasure and then sacrifice it for mana while you pay, because the cost is locked in first (601.2f and 601.2g).
Does affinity reduce commander tax?
Yes. The tax is generic mana added for each previous cast from the command zone (903.8), and increases are added before reductions are taken off (601.2f), so affinity reduces the tax like any other generic mana.
Is a spell made free by affinity still cast?
Yes. You cast it and pay a total cost of {0}, and paying a reduced cost "counts as paying the original cost" (118.7), and it becomes cast like any other spell (601.2i). It triggers anything that cares about a spell being cast, and it counts toward storm.
Build an artifact deck that pays for itself
Open a list in the deck builder and count your artifacts: affinity is only as cheap as that number on the turn you cast the spell. Artifact lands count too, and the lands calculator tells you how many lands the deck wants. Grover can take a brief such as "an Emry deck that casts its affinity spells for one blue mana" and propose cards in plain language, and Scry searches on what a card does, so you can ask it for spells that cost less for each artifact you control.
Create a free Mana Grove account to build with the full deck builder and format legality checks, see plans and pricing for more time with Grover, Scry and Tutor, and read the rest of the MTG keywords and mechanics glossary, where improvise, the other way artifacts help pay for a spell, is listed too.
Sources
- Magic: The Gathering Comprehensive Rules, effective September 25, 2026: https://magic.wizards.com/en/rules. Read on October 26, 2026. Rule 702.41 (Affinity) is quoted above, and rules 109.2 (a card type in rules text), 111.10a (Treasure tokens), 118.7 and 118.7a (cost reductions), 202.3 (mana value), 601.2f to 601.2i (determining and paying the total cost, and the spell becoming cast), 903.5d (basic land types in a Commander deck) and 903.8 (the commander tax) are cited.
- Mana Grove card database, read on our card pages on October 26, 2026: the mana cost, type line, rules text and Commander legality of every card named above.
- Official card rulings, MTGJSON build of October 24, 2026: affinity reduces only generic mana, it doesn't change a spell's mana value, and several instances of affinity on one spell each apply.
This article is updated when the Comprehensive Rules change the affinity entry or when a set adds an affinity card worth listing. The date at the top is the last revision.
