Harness in MTG: Rules, History, and Best Cards

The Soul Stone | Illustration by Volkan Baga

The Infinity Stones are some of the most powerful artifacts in the Marvel universe, and Magic has tried its best to translate their power into MTG mechanics.

How? By requiring you to harness their power, which isn’t as easy as just casting them. But worry not! Harness isn’t that difficult, either!

Let's find out how it works in MTG, and how can you tap into the Stones' infinite abilities.

How Does Harness Work in MTG?

The Mind Stone | Illustration by Volkan Baga

In Magic, harness is a keyword action that changes the status of a permanent. When an effect tells you to harness a permanent, that permanent becomes harnessed.

Harnessed is just a designation that doesn't do anything more by itself. A harnessed permanent doesn’t automatically become stronger. Other text on the card has to care about the permanent being harnessed. That “other text” is what's written on the card as its ∞ ability.

For example, The Soul Stone has an ∞ ability that only matters after it's been harnessed.

A permanent stays harnessed until it leaves the battlefield. If your harnessed Infinity Stone is bounced, exiled, or otherwise moved off the battlefield, it stops being the same object. If it later returns, it returns unharnessed.

On the other hand, removing abilities from a harnessed permanent doesn’t remove the fact that it’s harnessed. It may remove the ability that cares about being harnessed, but the designation itself remains.

And a very niche thing for the rules lawyer among you: Being harnessed isn’t a copiable trait. If you copy a harnessed The Soul Stone, the copy won’t automatically be harnessed. It needs to be harnessed separately.

The History of Harness in MTG

Harness debuted with The Soul Stone in Marvel’s Spider-Man, and the next harness card was The Mind Stone from Marvel Super Heroes.

Harness is very much not an evergreen mechanic, which are common mechanics we see in every MTG set. Thus far, ∞ is only found on Infinity Stones from Marvel sets. In theory, WotC could release other harness-able permanents… but I think it's a very safe bet that harnessed will be reserved for the Marvel IP.

Can You Harness at Instant Speed?

Yes, with the existing harness cards, you can harness at instant speed.

The Soul Stone and The Mind Stone each have an activated ability that lets you harness them. You can normally activate abilities any time you have priority (unless the ability says otherwise).

Future harness cards could work differently, though! A future card might say “Activate only as a sorcery,” or harness a permanent on ETB, or use harness in some other restrictive way.

Can You Harness Multiple Times?

Yep, you can! But a permanent can only become harnessed once, and there's no way to remove the harnessed designation (not even if a permanent loses all abilities), so at the moment there really isn’t much point harnessing a Stone multiple times.

In other words: Yes, you can activate The Mind Stone’s harness ability again after it’s already harnessed (assuming you can untap it and pay the cost again, of course). But you won’t get a second harnessed designation. You won’t get two copies of the ∞ ability. You won’t make the trigger happen twice.

What Does the Infinity Symbol on Harness Mean?

The ∞ symbol is the visual marker for a special ability on Infinity Stones. It means: “This permanent has the listed ability only when it’s harnessed.”

Keep in mind that the ∞ ability itself isn’t the same thing as being harnessed. Harness is the action; harnessed is the designation; the ∞ symbol is the stuff that happens if/when the permanent is harnessed.

Before the permanent is harnessed, the ability after ∞ isn’t available. After the permanent is harnessed, that ability functions like normal rules text on the permanent.

This also means normal rules still apply to the unlocked ability. If the ∞ ability is a triggered ability, it uses the stack. If it targets something, it needs a legal target. If the target becomes illegal before the ability resolves, the ability won’t affect that target.

Can You Counter a Harness Ability?

Yes, you can! And in more ways than one, actually.

For starters, you can counter the ability that harnesses a permanent with Stifle, Disallow, or similar cards that counter activated abilities. Counterspell won’t counter a harness ability, because harness abilities aren’t spells.

With the above, you've prevented me from harnessing my Infinity Stone. But even if I manage to harness it, you can still counter the ∞ ability's trigger on the stack with effects that counter triggered abilities.

Lastly, you can remove abilities from a permanent. It won't “de-harness” a harnessed permanent, but removing my Stone's abilities either prevents me from activating the harness ability or neutralizes the ∞ ability itself.

Can Mana from the Infinity Stones Be Used to Harness Themselves?

Yes, it can.

But the tap symbol is a hurdle. Both The Soul Stone and The Mind Stone have a mana ability that requires tapping the artifact. And their harness abilities also require tapping the artifact.

But if you can untap them after you’ve floated their mana, then yes, you can use it to activate their other ability.

What Is the “Origin” Ability on MTG Arena?

For reasons that we'll never fully know (most likely some licensing kerfuffle between Hasbro and Disney), when Spider-Man was released, MTG Arena and MTGO got the Through the Omenpaths version: same cards, same abilities, but different names and art.

The Terminus of Return is the in-universe version of The Soul Stone. Instead of being a Marvel Infinity Stone, it uses Magic’s own creative treatment. And The Terminus of Return uses origin rather than ∞.

Exactly the same thing, just “translated” from a Universes Beyond set to a digitally-only MTG set.

As of May 2026, the point has become mostly moot as Disney and Hasbro resolved their licensing differences, bringing the full SPM set to MTG Arena (ability names included!).

Will Harness Be Used Outside Marvel Sets?

I very much doubt it.

Mechanically, there’s nothing about harness that requires a Marvel setting. A future Magic set could use harness on ancient machines, sealed relics, sleeping gods, dormant portals, or other objects that need to be “powered up”.

But from a flavor perspective, I think it's very likely that we'll only see harness in Marvel sets. And probably only on either the remaining Infinity Stones, or on cards that are made to interact with them.

Gallery and List of Harness Cards

• The Soul Stone
• The Mind Stone

Best Harness Cards

The Soul Stone

The Soul Stone is an excellent black mana rock, and it has the track record to prove it. It's the most popular SPM card in casual Commander decks by a good margin, it shows up occasionally in decks in Standard, Pioneer, and cEDH, and perhaps most importantly: If you consider only regular versions, it's one of the most expensive new cards printed in 2025.

WotC seems to have followed the same playbook as with The Lord of the Rings, making the main McGuffin a really good card!

The Mind Stone

The Mind Stone definitely looks weaker than The Soul Stone: Blinking your permanents is certainly something that some white-leaning decks love, but it’s a lot weaker than a once-per-turn reanimation effect.

It's still the second-best harness card out there, though!

Wrap Up

The Soul Stone | Illustration by Volkan Baga

And that's about it for harness, harnessed, and the infinity symbol!

Long story short: A ∞ ability gets “turned on” whenever the permanent becomes harnessed, simple as that. The only complexity is that the ∞ ability isn’t the same as harnessed (harnessed is a designation that makes the ∞ ability come online, so to speak).

I hope you've enjoyed this mechanical deep dive into Magic's harness mechanic, and if you have comments or questions please drop one below, or stop by the Draftsim Discord for a chat. For more Magic in your inbox daily, subscribe to our newsletter.

And good luck out there!