You're using my memories and feelings against me in the dream state. But you forgot one important thing... One thing you couldn't possibly know. Krypton died, and I went to sleep. I slept for decades. I learned how to control my dreams. 
Adventures of Supergirl #3 is an issue of the series Adventures of Supergirl (Volume 1) with a cover date of August, 2016. It was published on June 8, 2016.
Synopsis for "Nightmare on El Street"
Supergirl is trying to to pry information from Vril Dox, backed up by a D.E.O. squad. All of sudden, Vril and the D.E.O. agents turn into monsters and shoot Kryptonite weapons at her.
Kara wakes up in her bed at home, feeling shaken by the fourth bad night in one week. A text message tells her to turn on the news, and Kara finds out that the D.E.O. command center has blown up, and Director Henshaw and her sister Alex have died.
Kara collapses and all of sudden she is in the middle of the the ruins of the D.E.O.. Her sister and friends has been turned into zombies and lash out against her physically and verbally. Kara realizes they aren't real and takes them out. Realing someone is trying to kill her in her dream, Supergirl takes off, demanding her attacker to show themselves.
Nonetheless, her dream changes abruptly and she's again a little child having dinner with her parents back on Krypton. Kara refuses to give in and declares she was sleeping for decades before arriving on Earth and learned how to control her dreams. Supergirl rips the dreamscape fabric and starts hunting her assailant.
Kara fights her way through different dreams. In one dream she is fighting the hordes of Nightflame in the Innerverse.[1] In another dream she is a teenager defending the Earth against thousands of Kryptonians together with her cousin.[2] In another dream she's an angel with fire wings fighting monsters. In another dream she defends Chicago from giant robots in the year 2965. In other dreams she fights versions of herself like a Red Lantern Supergirl[3] or a t-shirt-wearing Kara.
Every time Supergirl catches a glimpse of her real enemy, though, her assailant changes the dreamscape and forces her through another battle. Kara never stops fighting and hunting her down, though, and after hundreds of dreams, Supergirl rips through one final barrier and breaks through her enemy's mental barriers.
Her psychic aggressor calls herself Psi, dream mistress of Fort Rozz, and claims Supergirl is a monster who must be put to sleep forever. Psi tries to throw Supergirl back into her head and into another dream where she is Kara Starikov fighting in World War II. Supergirl breaks free and confronts Psi again.
Psi reveals she was a Fort Roz psychic guard whose job was to watch and keep dangerous criminals asleep, but whose physical body was destroyed when Fort Rozz crashed into Earth. Psi empathized with Rampage and accuses Supergirl and her sister Alex of killing Rampage and her sister. Kara argues she honestly tried to save Rampage and dares Psi to really look into her mind.
Psi learns the truth and wonders if Facet lied to them all. Supergirl wants to Psi tell her more, but Psi decides to release her under the condition that Kara promises to help her.
Kara promises to do so, and she finally wakes up. Kara calls Alex to tell her sister they have a new mission.
Appearing in "Nightmare on El Street"
Featured Characters:
Supporting Characters:
- Department of Extranormal Operations (In dream sequence only)
- Hank Henshaw (In dream sequence only)
- Alex Danvers (In dream sequence only) (Phone call only)
- Agent Stern (In dream sequence only)
- Hank Henshaw (In dream sequence only)
Antagonists:
- Facet Jens (Behind the scenes) (Mentioned only)
- Red Tornado (Mentioned only)
- Vartox (Mentioned only)
- Nightflame (Mentioned only)
Other Characters:
- James Olsen (Mentioned only)
- Winn Schott (Mentioned only)
- Astra (Mentioned only)
- Cat Grant (Mentioned only)
- General Sam Lane (Mentioned only)
- Alura (In dream sequence only)
- Zor-El (In dream sequence only)
- Zal-Tel (Mentioned only)
- Thought-Beasts (Mentioned only)
- Babootches (In dream sequence only)
- Supergirl (Earth-One) (In dream sequence only)
- Supergirl (New Earth) (In dream sequence only)
- Linda Danvers (In dream sequence only)
- Red Lantern Supergirl (Prime Earth) (In dream sequence only)
- Kara In-Ze (In dream sequence only)
- Kara Starikov (In dream sequence only)
- Superman (Mentioned only)
- Mar (In dream sequence only)
Locations:
- Earth
- United States of America
- California
- Illinois
- Chicago (Mentioned only)
- United States of America
- Krypton (In dream sequence only)
- Fort Rozz (Flashback only)
Items:
- Green Kryptonite (In dream sequence only)
Vehicles:
- Kryptonian Rocket (Flashback only)
Trivia
- Some books on Kara's nightstand are a homage to DC writers like Paul Kupperberg and Carmine Infantino.
- Zal-Tel was the name of a Kryptonian artist who mentored Zor-El and his daughter in New Earth continuity. "Tanth" was an honorific used by Pre-Crisis Kryptonians.
- Thought-Beasts and Babootches are Kryptonian animals.
- Supergirl's apartment building Hammersmith Tower shares name with the building where Lana Lang and Supergirl lived in Post-Crisis continuity.
- Kara's dreams are a callback to different storylines like Superman: New Krypton, Supergirl: Red Daughter of Krypton or DC Bombshells.