Why Did the Jedi’s Lightsabers Keep Shorting Out on THE ACOLYTE? STAR WARS’ Cortosis, Explained

The Acolyte‘s fifth episode revealed the identity of Mae’s dark Master, but the person underneath that mask wasn’t the only fascinating thing we learned about that helmet. Qimir’s terrifying headgear on The Acolyte is made from cortosis. But what is cortosis exactly? Well, cortosis is a legendary material from Star Wars lore. That powerful, rare metal can withstand blows from a lightsaber and even cause them to short circuit, as we saw on The Acolyte’s fifth episode. Without that helmet, the Jedi might have stopped their most dangerous enemy. But more worrisome than what it can do in battle is what the presence of a cortosis helmet indicates about the danger the Jedi now face.

What Is Cortosis, the Metal Qimir Used to Make His Helmet on The Acolyte?

The masked Master with his hand out while holding a red lightsaber in the other on The Acolyte

Qimir wears a cortosis helmet on The Acolyte. Cortosis is an uncommon metal that is among the strongest and strangest in the galaxy far, far away. It’s found on two Star Wars planets: the Mid Rim planet Dinzo and the Outer Rim planet Mokivj.

Cortosis is extremely fragile unless refined. Then, it becomes incredibly powerful. Timothy Zahn’s Thrawn: Alliances explained why. The rare metal has an “unusually high energy absorption and transmission coefficients.” That allows cortosis to “dissipate” energy blasts along fibers without damaging them. While cortosis has its limits, notably lengthy energy attacks, it still poses a unique problem for Jedi fighting a dark side user.

Cortosis Can Short Out Jedi Lightsabers, as We Saw on Star Wars: The Acolyte

In short, refined cortosis can withstand a lightsaber blast while causing the weapon to short out. Qimir used his helmet to do both while fighting multiple Jedi on Khofar. His helmet provided a shield that blocked lightsaber strikes, allowing him to fight in a unique style. It also made the Jedi weapons temporarily malfunction and shut down. Those brief moments bought Qimir extra time to defeat his confused, briefly unarmed opponents.

Without his cortosis helmet, Qimir likely would have died on that planet in The Acolyte‘s fifth episode. Master Sol bested Qimir after the dark Master lost his mask.

Star Wars‘ official website shares, “Cortosis is not particularly strong. In its purest state, it can easily be fractured, which means the metal is not as durable as beskar — illustrated by Jecki Lon’s fierce takedown of the Stranger’s cortosis helmet in The Acolyte. However, its unique ability to absorb, dissipate, and transfer energy makes it a valuable tool against blaster fire, and even lightsaber blades. In fact, cortosis will temporarily short out a lightsaber upon contact, making it a potentially surprising shielding material that renders a Jedi vulnerable.”

The Acolyte Reveals That Cortosis Can Also Be Used for Sensory Deprivation

Osha wearing Qimir's mask on The Acolyte

The Acolyte reveals that cortosis can be used for more than just shorting out lightsabers, though. It can also be used to create an experience of sensory deprivation. Qimir notes that his cortosis helmet is handy against lightsabers, but is also a “sensory deprivation headpiece,” like the Jedi use as Younglings. He notes that while wearing a cortosis headpiece not only are all your senses blocked, but “It’s just you and the Force and what you bring with you.”

Star Wars the acolyte cortosis helmet

Where Is Cortosis Mined?

Osha touches Qimir's mask on The Acolyte

The Acolyte also reveals where cortosis is mined, sort of. Qimir lives on an “Unknown Planet.” That planet really reminded us of Star Wars‘ Ahch-To, but it turns out that it’s really a planet where cortosis is mined. Cortosis is a rare metal, so it’s not found many places in the Star Wars universe. We’ll have to wait for The Acolyte to reveal which planet this is exactly and what other secrets it holds.

Showrunner Leslye Headland notes, “the idea is that cortosis is mined on this planet, so I don’t think that’s the case with Ahch-To. Part of the reason this is his home base is that cortosis is a very rare metal. I don’t think we say it explicitly in the show, but that’s a reason it’s not Ahch-To.”

When Was Cortosis First Introduced in Star Wars?

The Acolyte Star Wars villain Sith Lord

Cortosis dates back known to the franchise’s non-canonical, pre-Disney “Legends” era. It notably appeared in Star Wars: Knights of the Old Republic and Darth Bane stories. There cortosis was best utilized as an anti-lightsaber weapon that also caused them to short circuit.

Ten years before The Acolyte, Cortosis made its canonical Disney-era Star Wars debut in 2014 in John Jackson Miller’s novel New Dawn. In its new form, it still closely resembles the original Legends iteration in terms of both properties and uses. Cortosis’ new canonical history also traces back millennia to the Era of the Sith. That’s when Star Wars’ legendary Null Blade was created to fight against the dark side order. During the Clone Wars, Count Dooku also used cortosis to create a protective shield that he employed against the Republic. And a possessed Doctor Aphra even used the Null Blade in a battle with Darth Vader.

What Does Qimir’s Use of Cortosis Mean for The Acolyte?

Qimir holds two red lightsaber blades on The Acolyte

The Jedi haven’t faced a real threat in so long that they didn’t even know what Qimir was. He had to tell Sol they might call him a Sith, an enemy no Jedi has seen for thousands and thousands of years. Qimir was too much for them. Yord said he showed a flagrant disregard for the “rules” of fighting. That included how he used his cortosis helmet, which rendered The Acolyte‘s Jedi weaponless and defenseless.

With his helmet back in hand, Qimir once again has something that can help him defeat Jedi. But more than that, his cortosis helmet shows he knows secrets from Star Wars‘ past that the Jedi have long forgotten. They couldn’t stop him when he only had a helmet on. What if he also found other uses for cortosis that they don’t know about?

Mikey Walsh is a staff writer at Nerdist and lover of fictional metals. You can follow him on  Twitter and  Bluesky at @burgermike. And also anywhere someone is ranking the Targaryen kings.

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