After the vicious murder of her adoptive parents, Carmilla discovered her biological mother, Monica Rappaccini, is the Scientist Supreme of the worldwide terrorist network A.I.M. (Advanced Idea Mechanics). Carmilla is now trying to find her real mother under the auspices of S.H.I.E.L.D., who are attempting to use her to infiltrate A.I.M. She appears in Incredible Hulk #87, a one-shot story that takes place immediately after House of M. Peter David, who wrote her appearances in Hulk, made suggestions that Bruce Banner may be her biological father.
Carmilla and her S.H.I.E.L.D. handler, agent Derek Khanata, had been sent to New York under orders to track down and capture The Uni-Power before it could fall into the hands of the terrorist organization A.I.M. Watching over the spot where a Captain Universe empowered Daredevil fought four Class Three A.I.M. Commandos, Scorpion and Khanata waited to see if A.I.M. (who was also at the site) would find anything. A group of kids interrupted the A.I.M. Agents work and were nearly killed until Laura Kinney a.k.a. X-23 stepped in. The A.I.M. Commandos who fought Daredevil before begin to assault X-23 when she becomes Captain Universe. Scorpion entered the fray, helping X-23/Captain Universe defeat the Commandos. Soon afterwards X-23 began to search for a hidden base. Scorpion joined her so that she could capture Captain Universe and get the information on it from A.I.M., however X-23 convinced Scorpion to see the light and let Captain Universe go. X-23 took Captain Universe to a safe hiding place while Scorpion brought an A.I.M. scientist back to S.H.I.E.L.D. for interrogation.
Carmilla has been identified as one of the 142 registered superheroes who appear on the cover of the comic book Avengers: The Initiative #1.
In Spider-Man Family #3 (set prior to Civil War: Choosing Sides #1) she appears in a short story again written by Van Lente and drawn by Leonard Kirk. Here she is infiltrating the unregistered superhero underground for S.H.I.E.L.D., and is sent on missions to establish a presence as a superhero. When the current Venom and former Scorpion Mac Gargan finds out about her, he challenges her to a fight, since he is negotiating for a movie based on his life story and does not want her diluting his trademark. She defeats him by absorbing some of his webbing, creating a "neo-symbiote" which disintegrates after she has defeated him.
Carmilla is seen trying to aid S.H.I.E.L.D. upon the Hulk's return. When she finally got to battle the Hulk, she filled his body with a S.H.I.E.L.D.-devised poison concoction specially designed to kill him, but the sole effect was to cause boils to erupt on his skin. The Hulk's healing factor returned him to normal after just a few minutes, after which he was prompted to a sudden rush of anger by Amadeus Cho. Cho reveals to her the relationship her mother and the Hulk had back when they were in college. Cho asks her if she thought about the origins of her green hair. Carmilla attacks a S.H.I.E.L.D. truck transporting Bruce Banner to his underground prison, destroying the truck and knocking out both agents. Intending to get a DNA sample from Banner, she opens his casket, only to discover it was one of three decoys.
It is revealed that Carmilla is now Hardball's lover and is the co-leader of the HYDRA Training Facility in Madripoor that the Shadow Initiative is supposed to be taking out. Carmilla and Hardball confront the Shadow Initiative along with an army of HYDRA agents shortly after learning they were searching for Hardball and has them pinned down in an old alleyway somewhere deep within the slums of Madripoor. It is later revealed that she was actually working undercover for an unknown source, implied to be Nick Fury. She convinces Hardball to turn himself in and escapes, but not before secretly stealing his S.P.I.N. Tech dart while kissing him.
Carmilla appears in a new costume during The Gauntlet storyline. She reveals that after quitting S.H.I.E.L.D., she began taking independent contracts. She was hired by Kraven the Hunter's family in order to steal Mac Gargan's original costume from The Hood (who had received the costume from Norman Osborn), who is planning to give the Scorpion costume to the low-level crook that impresses him. The Scorpion stings Spider-Man and he temporarily loses his powers. She then proceeds to fight The Hood and his allies and is quickly overwhelmed. However, Spider-Man regains his powers and saves her. She then delivers the suit to Sasha and Ana.
Genetically designed by her "mother" as part of a group of similar kids called Wakers that were designed to be immune against environmental toxins, Scorpion mutated - greatly heightening her comparative abilities and equipping her with a left arm that allows her to release filtered toxins at her will.
Her lymphatic system produces a “ludicrous” variety of life-saving chemicals, for example atropine to defend against nerve gas or amyl to overcome blood agents like cyanide. Her sweat glands excrete dimercaprol and chloramine to counteract blistering agents such as mustard gas. Her cell nuclei float in a solution of iodized salt to deflect gamma rays and other radiation. Like activated charcoal, the cilia lining Scorpion's trachea are highly absorptive, neutralizing harmful particles before they reach the lungs. The axillary node in her left armpit is unusually swollen. Toxins seem to be accumulating there, to be released along the arm and hand. Since lymph fluid absorbs the chemicals it fights this is highly dangerous. This absorption ability is potent enough to assimilate even the toxins that compose the Venom symbiote; the symbiote fled, fearing that she may be capable of truly destroying it.
Essentially her unique body chemistry makes her immune to most types of poisons and unhealthy chemicals, gases, radiation (in fact she can absorb and possibly gain nutrients from them), and diseases. She is even capable of overcoming poisons designed to be allowed in by the other members of the Wakers and in fact the mind controlling chemicals meant to make her loyal to her mother's agenda were what she originally absorbed and accidentally used to kill her boyfriend. She's physically gifted since her body's chemistry keeps her in top physical shape regardless of what she ingests.
Originally uncontrolled and resulting in her boyfriend's death at the prom, after 3 years she's gotten relative control over it and can alter the strength of her poisonous touch from making people sick to knocking someone out to killing them. She also gained nearly indestructible mind controlled gauntlets packed full of SHIELD technology and a body suit that manages to stop most if not all weapons and has other built in gadgets.
Since Madripoor she has added a tail (similar to Mac Gargan's) to her costume with a stinger that injects S.P.I.N. tech nanites after ingesting the contents of the dart that she stole from Hardball. The effects only last half-an-hour. Since she said the source of the nanites is her body it is hinted that unlike the previous Scorpion, her tail might be semi-organic.
There's also evidence that she may have honed her skills as a thief in the three years she was on the street.
In the House of M reality, the Scorpion was raised by her mother, and has a good relationship with her (as she was never adopted, she also goes by her birth name of Thasanee Rappaccini, although she retains the Scorpion codename). She is thus an agent of the semi-heroic AIM, and helped recruit the Hulk, her mother's former lover, to overthrow Exodus' totalitarian Australian government.The name Rappaccini is an allusion to the short story "Rappaccini's Daughter" by Nathaniel Hawthorne. The title character of that story is a beautiful young woman whose breath and touch have been rendered poisonous by the experiments of her father.
Scorpion was originally intended to be the daughter of Silver Samurai and Viper, explaining Carmilla's hair color.