The Avatar: The Last Airbender Technique In The Justice League Snyder Cut
On its surface, Avatar: The Last Airbender doesn't seem to have much in common with Zack Snyder's Justice League. Both tell stories about superpowered beings, sure, but they're set in entirely different worlds and aren't exactly a match in tone. Although Aang (voiced by Zach Tyler Eisen) probably wouldn't handle himself well against Darkseid, there is one tactic in the Snyder Cut that seems to be ripped almost directly from a technique used at various points in the Avatar timeline.
The technique in question is used by an Mera (Amber Heard), one of the Atlanteans who is attempting to protect the mother box that's been given to her people. During the scene, Mera seems momentarily able to take down Steppenwolf (Ciarán Hinds), even though he ultimately overpowers her. In order to stop him from stealing the box, she employs a technique that is likely to be familiar to fans of Avatar, especially if they remember the horrific episode where Katara (Mae Whitman) learns to bloodbend.
Minor spoilers for Zack Snyder's Justice League ahead
How Mera uses Steppenwolf's blood against him
During the initial phase of the battle, Mera saps the water from a massive space around Steppenwolf as he heads toward the mother box. This ultimately causes him to fall deep into the cavern holding the magical item. Once he's recovered, he pins Mera against a wall. It's at this moment that she uses the technique that resembles bloodbending. She removes the water from the space surrounding Steppenwolf's head, and then appears to pull the water and blood right out of Steppnwolf's body.
It's a move that weakens him severely, although he ultimately manages to recover enough to make off with the second mother box. Mera gets this moment to display her strength before Arthur (Jason Momoa) steps in to lend a hand. Even together, they don't have enough power to stop Steppenwolf. It's at this moment that Arthur realizes he may need to join the Justice League, even though he was reluctant to at the beginning of the film.
Bloodblending is a taboo in the world of Avatar
Although it's unclear how controversial Mera's technique is among the Atlantean population, a very similar technique is depicted as being something like a dark art when it's used on Avatar. On that show, it's called bloodbending, and it's a specialty that highly skilled water benders can develop. The technique allows its users to control other people's bodies by manipulating the water in the blood that runs through their veins.
Although Mera doesn't use her technique to manipulate Steppenwolf, it seems possible that she could. In the world of Avatar, doing something like that is seen as an act of evil, although it's ultimately justified under severe circumstances. Bloodbenders can only perform the forbidden technique under the light of the Full Moon, whereas Mera's skill doesn't seem subject to the same limitation.
Even if there is a similar taboo in the world of the Snyder Cut, it seems likely that the Atlanteans would probably make an exception for Steppenwolf.