Continuing last week's report, this week American comic expert POPO will continue to introduce "Quicksilver" and "Scarlet Witch," two major characters appearing in "Avengers: Age of Ultron," to all toy enthusiasts. If you want to learn more about their backstories, follow along with us!~
After the House of M event, Pietro, having lost his superpowers, felt disheartened and believed he was the genocidal killer responsible for the mass extinction of mutants. At this point, an enraged Spider-Man came to punch him, because in the false timeline of House of M, the deceased Gwen had become his wife, and Uncle Ben was still alive. Feeling that his deceased loved ones had been toyed with, Spider-Man vented his anger on the powerless Pietro, but later understood Quicksilver's mindset and calmed down. However, Quicksilver, feeling guilty, wanted to commit suicide by jumping off a building, but was rescued by his ex-wife Crystal, who appeared and took him to the Inhumans' stronghold for healing. 
In Inhuman tradition, newborns must enter the Terrigen Mists, allowing the mist to integrate with the Inhuman's genes, thereby triggering various superpowers. Pietro then conceived the idea of entering the mists, but Blackbolt, the King of the Inhumans, refused on the grounds that Pietro was not an Inhuman, as human contact could have adverse effects. Nevertheless, Pietro secretly snuck into the Terrigen cave, but no immediate effects were shown, so he returned disappointed. 
Upon returning to his residence, Pietro found an older version of himself there. It turned out the Terrigen Mists had enhanced his superspeed, allowing him to leap through time to 14 days in the future, but it also caused Pietro to age in appearance. Pietro then decided to absorb more Terrigen Mists to stabilize his abilities, seizing the Terrigen Crystals that generated the mist. This also granted his daughter, who had not undergone the mist's baptism at the time, the superpower to perceive others' emotions. Afterwards, Pietro absorbed all remaining crystals, intending to give them to the depowered mutants. 
However, Blackbolt's fears came true. Many mutants, due to the mists, had their powers excessively amplified; some mutants with sensory-based abilities felt rain like knife cuts. Magneto, who had regained his powers after a battle with the Avengers, came to stop his son and rescue these mutants, but doctors said these abilities were only temporary. After discovering the crystals were stolen, Blackbolt contacted the Fantastic Four. The government also learned of the Terrigen Crystals' existence at this time and, wanting to prevent another mutant-like race from causing social unrest, joined the scramble to acquire them. Blackbolt communicated with the U.S. government, but the outcome led to war.
Pietro then reunited with his old friend Multiple Man, with whom he had previously worked in the X-Factor department. However, a conflict ensued, knocking all the crystals out of his body. Pietro once again lost his superpowers and was imprisoned. But when he saw a woman being attacked, whether due to residual mist influence or other reasons, Pietro regained his superpowers, rekindling the heroic mindset he had when he first joined the Avengers, and once again became "Quicksilver."
Hawkeye, who was originally killed by Scarlet Witch during the Avengers Disassembled event, was resurrected in the mainstream world because he was alive in the false reality of House of M. He joined the New Avengers, who were evading forced registration by government authorities, but also intended to search for the missing Wanda. He found Wanda at the foot of Mount Wundagore, where their twins were born. However, Hawkeye discovered she was living happily and had no painful memories of the past, so he chose to leave her to live her new life. 
The Skrull's Secret Invasion plan failed, leading to the Dark Reign era where Green Goblin Norman Osborn controlled superhuman affairs. Ant-Man, in memory of his wife Wasp, whom he believed to be dead at the time, renamed himself Wasp and formed his own Avengers team. Quicksilver, seeing Wanda among this Avengers team, also wanted to join, but Wasp refused. However, to prove himself, Quicksilver continued to participate in this Avengers team's operations and even retrieved some Terrigen Crystals for the Inhumans.
Quicksilver claimed to the Inhumans that it wasn't he who stole the crystals, but a Skrull imposter. Since the Inhumans had also suffered greatly from distrust among their own kind during the Secret Invasion, they believed his story. However, Wasp and Quicksilver's daughter knew the truth, but due to their father-daughter and friendship ties, and recognizing Quicksilver's desire for atonement, both chose not to expose him to give him a chance. 
Later, everyone discovered that the Scarlet Witch in Wasp's Avengers was actually Loki in disguise. An agitated Quicksilver even clashed with Thor over this. Subsequently, Wiccan, a member of the Young Avengers team, once used his reality-altering powers while fighting terrorists, causing tension for the Avengers. Wiccan and his teammate Speed were sought out by Magneto, who believed them to be the reincarnations of Wanda's children, his own grandchildren. He accompanied the entire Young Avengers team in their search for Wanda. Through Hawkeye, they learned Wanda's last known location, but it turned out to be a robot. Everyone speculated that Doctor Doom was the mastermind, so they traveled to the country he ruled.
It was then that past secrets were revealed: when Scarlet Witch lost her twins, she had already sought help from Doctor Doom, who was proficient in both technology and magic. The two summoned the Entity, which governs life within the cosmic consciousness (cosmic gods), to possess Wanda. The Entity then released the twin souls controlled by Mephisto, who were reincarnated as the current Young Avengers members Wiccan and Speed. 
However, Scarlet Witch herself was unaware, and thus gained her reality-altering powers, which led to the Avengers Disassembled and House of M events. All of this was part of Doctor Doom's conspiracy, as he sought to control the Entity's power, mastering life and death, to use it as leverage to control the world. Ultimately, his ambitions were thwarted through the cooperation of the X-Men, Avengers, and Young Avengers. Afterwards, Wanda refused to return to the Avengers or participate in family gatherings, wanting to be alone for a while, and so she left first.
Quicksilver then became a teacher at Avengers Academy, speaking about second chances. However, one student, Finesse, also learned of Quicksilver's lie about blaming the Secret Invasion. Her condition was for him to teach her everything he knew, and she even spoke in Quicksilver's defense in front of Magneto. Wanda and Pietro later intervened in many major events. Even though they had made grave mistakes, they continuously reflected on themselves, not just for atonement, but as a decision to continue protecting the people.
Further Reading:
"Avengers: Age of Ultron" Must-Read Before Release! Two New Characters You Absolutely Need to Know! - Part One
"Avengers: Age of Ultron" Must-Read Before Release! Do You Know Who the Main Villain 'Ultron' Is?