The second Ant-Man movie showed that Janet was able to cure Ava Starr, aka Ghost, with the use of healing powers. Loveness explains that Ant-Man and the Wasp: Quantumania was originally going to dive deeper into how exactly Janet developed those powers and how they worked.
van Dyne healing Ava Starr After absorbing quantum energies at an unprecedented rate, van Dyne was able to manipulate the structure of living organisms on the sub-atomic level and prevent them from experiencing quantum displacement; she could also reverse existing quantum displacement, as she did for Ghost.
As explained in Ant-Man and the Wasp, Ava Starr gained phasing abilities after her father's Quantum Tunnel exploded, causing her to become intangible for brief periods. Her powers cause her extreme pain and eventually, they will tear her apart.
Using the powers she had obtained through her long stay in the Quantum Realm, van Dyne transferred a significant amount of quantum energy into Ghost, thus temporarily stabilizing her condition and ending Ghost's campaign against Ant-Man and his allies.
She began plotting to harvest quantum energy to prolong her life. At the verge of dying, Janet van Dyne transfers some of her quantum energy to Ava, temporarily stabilizing her condition. With this, she slowly makes a recovery and goes into hiding with Bill.
Janet van Dyne Returns From the Quantum Realm | Ant-Man and the Wasp (2018) IMAX Movie Clip HD 4K
What is Ava Starr's weakness?
She has a weakness for the instability of a molecule in herself, which is painful and can cause death. So that way, Ava will need a quantum energy that is greater than the Quantum Realm to fully stabilize her condition.
Her masterful hand-to-hand combat skills and powerful “Ghost” containment suit hint at a past as an assassin or spy. Now, however, she's a rogue agent who works solely for herself. Ava's ability to phase through objects, turn invisible, and harness super strength makes her a formidable opponent.
When Janet went sub-atomic and entered the Quantum Realm in 1987, she stayed there for 30 years. Upon her return, it looked like she had aged 30 years. This would imply that even within the Quantum Realm, time doesn't work the same for everybody.
Janet van Dyne is usually depicted as having the ability to shrink to a height of several centimeters, fly by means of insectoid wings, and fire bioelectric energy blasts.
Speaking to THR, Reed shared that the reason Luis wasn't in Ant-Man and the Wasp: Quantumania was simply because the team knew they were going to go into the Quantum Realm early and feature a lot of new characters there. "There were no versions of this movie [with Luis]," Reed said.
Ghost's fate remains unknown after Ant Man & The Wasp after Thanos erased half of all life in the universe. Even if she was spared from the Snap, she would've ended up dying due to Scott being unable to return from the Quantum Realm.
With such a dramatic time span, the character obviously needed to be recast to accommodate Cassie's true age. Thus, Abby Ryder Fortson was replaced by Emma Fuhrmann to embody the teenage Cassie.
He met Janet van Dyne during that period of time and the two became lovers, as van Dyne had 'psychological needs' when she was stranded in the Quantum Realm.
The wife of Hank Pym and mother of Hope, Janet Van Dyne operated under the codename Wasp in S.H.I.E.L.D. but became lost to the Quantum Realm during a dangerous mission.
Michelle Pfeiffer's Janet Van Dyne may have had a physical relationship with Kang the Conqueror while they were both trapped in the Quantum Realm, and the pair may have even had sex. Ant-Man and The Wasp: Quantumania revealed that Janet wasn't alone when she was trapped in the Quantum Realm for many years.
Tony stark created a mapping system so they could find their way around the quantum realm, time is extremely abstract down there so 5 years could be 1 second or 80 years depending on where you would be.
Ant-Man and the Wasp's post-credits scene ended with Scott Lang being trapped in the Quantum Realm. This came as a result of Thanos' snap dusting Hope van Dyne, Hank Pym, and Janet van Dyne, making it impossible for them to pull Scott back out.
Like others from his native era, Kang ages at a slightly slower rate than modern humanity and is more resistant to the effects of radiation; though, he can be harmed by concentrated doses. He is an expert in time travel and the manipulation of time, and has mastered his future's advanced technology.
Kang the Conqueror was exiled to the MCU Quantum Realm by his own variants in the Council of Kangs due to his attempts to eradicate them and become the sole Kang in the multiverse.
What happened to Janet van Dyne in the Quantum Realm?
In the 2015 film, Ant-Man, it was revealed that during a mission, Janet was forced to shrink between the molecules to stop a ballistic missile. While her action saved lives, it also caused her to be lost for decades. Hank went years believing she was dead while silently hoping that there was a chance to bring her back.
When an experiment involving the Quantum Tunnel went wrong, Starr tried to run to her father to ensure he did not die alone, but the tunnel ruptured before she reached him, killing her parents and inundating her with quantum energy.
Despite neither character being one of the 36 characters present at Endgame's final battle previously confirmed, both Hannah John-Kamen's Ava Starr (AKA Ghost) and Tim Roth's Abomination (otherwise known as Emil Blonksy) were present at the Battle of Earth.
