But has there ever been a Ghost Cass AU?

Cass dies while on Patrol, maybe is was a villainous plot, maybe it was a random goon getting a lucky shot, maybe she was killed by somebody she trusted...maybe...

Whatever way she died, Cass ends up as a Ghost.

I can see 2 different paths this could take, depending on where she reforms:

PATH 1: Cass Reforms where she died

Cass is reformed where she died, probably very soon afterwards or a few hours later. The Batfamily have not had time to get over their Grief, they only just retrieved her Body an hour ago and need to go back to the crime scene to investigate.

And once they get there, they see what looks like Cass’s Orphan costume but colored differently, just sitting there in a daze. She just became a ghost, only a few hours after her death due to her exposure to the Lazarus Pits, and it was Jarring. Not to mention the Pure Ectoplasm she is made of is reacting weirdly to the corrupted Ectoplasm that is in Jason, making her anxious.

Meanwhile [Insert Batfam member] and Jason are confused, scared, and paranoid. [Batfam member] remembers reading a few articles in passing while researching Lazarus Pits. They were about the Ectoplasmic Entities made from Lazarus Water called Ghosts, how they are imprints of a human consciousness after an emotional death. They are also completely malevolent and non-sentient.

[Batfam Member] doesn’t hope to believe that this is Cass, all the research says that this is a pile of goop pretending to be her. Of course this makes them mad, not only is this thing wearing their sisters face, it will also probably hurt people when it gets strong enough using said face. It feels like an insult. And Cass can’t even defend herself to them, since she lost whatever was left of her ability to speak when she became a Ghost, and she is too dazed and weak to do Sign Language.

[Batfam Member] explains what they know about Ghosts to Jason, how this isn’t Cass at all, just an imprint of her memories. They say this right in front of her, which scares her since they don’t seem to consider her a person anymore, just a thing using Cass’s face

Back when they first read up on Ectoplasmic Entities, he made sure to get a small Ecto-Infused Knife for everyone in the Family in case they ever encountered one.

They bring it out, but before they can do anything, the Ghost of Cass recognizes it and runs away. 

Jason is mad that [Batfam Member] instantly went for the knife, or didn’t think to look for any second opinions.

Cass runs to the Batcave, but she gets there as [Batfam Member] is explaining what Ghosts are on the big screen to everybody else. She also sees her own body, laying on a table in the center of the room. She starts to believe that [Batfam Member] is right, that she can’t be the real Cass, just a reflection. And she can’t stay here, the others are bound the believe [Batfam Member] over her now

She runs away, not even revealing herself to her family.

She runs and runs and runs for hours upon hours, non stop, across state lines, until she reaches a place where her instincts were telling her to go. It feels like the air is clear, like she has more energy. She has made it to Amity Park.

From there you can go in any direction you want.

PATH 2: Cass Reforms in the Zone

Cass reforms in a random place in the Zone, in a color swapped version of her Orphan costume. She wakes up to see a sky of green and ground of purple, completely alone, no one around her.

She wanders for a bit, but a run-in with a Monster forces her to run. As it chases her, she finds that she can fly, but so can it.

As she is running, a blast comes from above her and blasts the monster away. She looks up to see a guy with Green-Blue Skin, pointy ears, and white hair, in a Black Hazmat Suit, floating above her.

He introduces himself as Phantom, and explains that she must be a Ghost. She can’t respond because she lost the last of her ability to speak, but thankfully he knows Sign Language

She can’t remember how she died, but she remembers most of the rest of her life. She takes off her mask, and you can see that she looks like normal Cass with Green Skin, white Hair, and the pointy ears. Also small fangs cause I think those are cool.

Danny helps her around, teaches her about the Zone, introduces his living friends, all that. She even meets a cute clone named Ellie, but that’s besides the point. Eventually, after a few weeks of traveling the Zone and learning about her new abilities, she asks if she can go see her family. Danny agrees, but says that first he should teach her how to shapeshift so she can look human enough to go to the living world.

Which is how Danny and Cass learn that Cass is a Halfa (due to her exposure to the Lazarus Pits). While she is thinking of her human form, a ring of gold energy surrounds her and she suddenly has a heartbeat again. She’s also extremely hungry cause Ghosts don’t need to eat, but Halfa’s do (even if it is significantly less)

By the time she goes to see her Family, they are not as high strung or paranoid as they would have been directly after her death, so they are more willing to listen to reason. Also with Danny there (and maybe ellie), he can explain what she can’t.

But now they don’t know what to do, they still haven't figured out who killed Cass, all they know is that she was definitely killed, it wasn’t an accident.