[3][4][5] The Rev-9 is a Terminator model developed by Legion, an artificial intelligence designed for cyber warfare in a future timeline where Skynet's rise gets prevented.

It manages to kill Diego and corner Dani and Grace, only to be temporarily disabled by the sudden arrival of Sarah Connor, who attacks it using high-grade weaponry.

By the time it is able to locate them again, they have allied with Carl, a T-800 Terminator left behind after Skynet's demise, and the Rev-9 is shocked by the encounter of a similar machine that not aligned with Legion.

The Rev-9 gives chase in a hijacked aircraft of its own, and manages to board theirs, leading to both Carl and the Rev-9 crashing into a river near a hydroelectric power plant while Dani, Sarah and Grace parachute to safety.

The explosion also destroys the Rev-9's liquid metal exterior, but its severely damaged endoskeleton continues pursuing Dani, who tries to use Grace's power source as an EMP against it, only to be held down and nearly killed until Carl reactivates and holds it back.

Once Dani stabs the power source into the Rev-9's endoskeleton, Carl drags it into a nearby pit, where the device's discharge melts both Terminators, destroying them.

[8] Rev-9 has a traditional solid endoskeleton covered with a liquid-metal exoskeleton, somewhat similarly to the T-X from Terminator 3: Rise of the Machines[9] and is considered a combination of the T-800 and the T-1000.

Its poly-alloy and endoskeleton can separate and fuse back together at a rapid pace, enabling it to split or merge during combat without ceasing its movements.

"[14] For example, in the film, the Rev-9 tries to convince the other characters to let him kill Dani, implying that he will show them mercy and let them go if they do, and tries to use logic to persuade the T-800 into joining him, stating that they were both built for the purpose of ending humanity.

[17] Luna said that the Rev-9's ability to learn and simulate human emotion ultimately becomes the character's weakness, stating that the Rev-9 grows frustrated with its failed attempts to kill Dani.

[19] Chris Klimek of Slate believed that the Rev-9, in its disguise as a villainous Border Patrol agent, was meant as an allegory on immigration issues between the U.S. and Mexico.

Like the T-1000 it is capable of shapeshifting to assume the appearance of anyone it touches and can morph its arms to form stabbing weapons and other shapes, such as hooks for scaling vertical surfaces.

[21] The Rev-9 can adapt behavioral responses (such as emotions) similarly to the T-800, either by choice or impulse, and its exterior can quickly heal itself after taking an injury, like the T-1000.