Larissa was observing Wayne Mansion when a gardener asked her what she was doing there, and she quickly took him out by jumping on his back and applying a rear neck choke. She then had him killed by her associates, rubbing his blood over her forehead and pretended to have been in a car accident which made Alfred let her in and try to help her. Selina and Bruce came down the stairs and Alfred realized she was a hired killer. The two got in a fight where her henchman distracted Alfred long enough for her to chase after Bruce and Selina. They lost Bruce and Selina who fled into the woods.
She was later seen looking for Dick Lovecraft and was confronted by James Gordon, she explained that if he stood down, she wouldn't kill him. James feigned surrender and then knocked out her henchman. She disarmed him and got into a fight with him after a short brawl, she quickly overwhelmed him and rendered him unconscious with a chokehold. She then used James' gun to kill Lovecraft.
She later got contacted by Clyde, a street criminal who had captured Bruce and Selina. She showed up with a team of henchman, Selina and Bruce tried to escape as Alfred and James showed up and got into a firefight with her henchman. She captured Bruce and asked him where Selina was. After he mentioned she was gone, she walked away when Alfred was getting close, though not before telling him he should not confuse bravery with good sense. 
As a ruthless mercenary, Larissa is willing to kill her targets. She is able to tactically deceive people and feigned helplessness to get close to her targets.
She seemed to uphold some code of honor, as she only killed people on the contract. Despite having the chance, she did not kill or seriously injure James and Bruce for standing in her way of performing her assassination.
- Peak of human physical condition: As a highly skilled assassin, Larissa is in top physical condition.
- Master hand-to-hand combatant: Larissa is highly skilled in unarmed combat, being able to easily take out a large man. She disarmed James Gordon and quickly beat him. She heavily relied on grappling moves and used choke holds to quickly render her opponents unconscious.
- Expert markswoman: Larissa is highly trained in the use of firearms.
- Although it hasn't been explicitly stated who sent Diaz after Selina, it can be inferred to be the Court of Owls due to their involvement in the Wayne murders and Lovecraft ranting to Gordon about "the people who control this city" wanting to him dead.
- Although Diaz remains unnamed during her first appearance in "Lovecraft", her real name and alias were revealed by DC Comics before the episode aired.
- Because she survived her first appearance, it was speculated by a DC Comics journalist that "we're sure to see her again." This assumption proved incorrect, although it is possible that she acts as a precursor to the characters who helmed the Copperhead mantle in the comics.
- In the comics, Copperhead is an alias utilised by multiple snake-themed supervillains. The original was a male contortionist of unknown identity who used his skills for assassin work. His successors were:
- This is the first live-action appearance of Copperhead. The Gotham version of Copperhead appears to be mainly based on the female incarnation of the character first introduced in Batman: Arkham Origins. The name Larissa Diaz was created specifically for Gotham, since the real name of the Arkham Origins Copperhead was never revealed.
- Dameron, Rebecca (writer) & Ferland, Guy (director) (November 24, 2014). "Lovecraft". Gotham. Season 1. Episode 10. FOX.
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