This is how Celestia's Umbrum possession goes in Return of the Umbrums.
[The claw moves backwards as it extracts her spirit from her body and Celestia's lifeless head goes down as her eyes close and her hair and tail stop flowing; Princess Celestia is now a floating bluish white protoplasmic head staring at her own lifeless body. She floats up and down with her hair floating at her sides while the claw holds her "tail" from behind. The claw slowly begins pulling Celestia's protoplasm back as she stares at her lifeless body and gasps in shock. She turns her head right, then left as she tries to turn to face the one controlling the claw]
Princess Celestia's protoplasm: Hey, put back my spirit thingy!
[The claw moves towards a vat]
Princess Celestia's protoplasm: That is so uncool!
[The claw ignores her pleas]
Princess Celestia's protoplasm: And you're messing up my hair!
[The claw stops moving and Celestia looks down and shows a bit of fear as she was only a few inches above the cauldron. She looks down to see that it was full of liquid and that in it was a small, slow moving, whirlpool of souls that seemed to go on forever. It soon became clear that they were about to put her in with the rest of the souls they had stolen from females]
Princess Celestia's protoplasm: You're a jerk! Capital J-E-…
[The claw quickly moves down and she lets out a cry as it dunks her protoplasm into the cauldron causing a small splash. She drowns in the sea of souls]
Princess Celestia's protoplasm: Erk!
[The claw emerges from the water, no longer holding onto Princess Celestia's protoplasm as it has its fingers apart. Afterwards an Umbrum climbs out of the cavern beneath the cauldron. The Umbrum grabs the edge of the platform and jumps up in front of the cauldron and walks past it as it snarls a bit. The Umbrum goes up to Princess Celestia's lifeless body with an evil grin as it chuckles deviously as it looks at her body. It grabs Celestia's chin with its left thumb and index finger and tilts her lifeless head up as it has its thumb on her chin. The Umbrum smiles evilly as it tilts Princess Celestia's head up and opens her mouth and chuckles evilly as it puts its right hand up while it holds her head up with its index finger under her chin as Princess Celestia's body moves upward. The Umbrum's right hand suddenly begins to evaporate and turns into a stream of mist that flows into Princess Celestia's mouth. The Umbrum growls a bit as its face then enters Celestia's mouth and Princess Celestia's body moves and twitches a little and her restrained front hooves move and her hair and tail start flowing again and her stomach makes strange noises as the Umbrum's body transforms into a mist that flows into her body through the mouth. The end of the stream enters Princess Celestia's mouth and Princess Celestia's body opens its eyes and stares forward with demonic expression, the Umbrum has possessed Princess Celestia's now vacant body. The Umbrum in Celestia's body turns its head as it looks around through the eyes of its new vessel]
[The two shadow guards standing at the sides walk up close and release the latches restraining Celestia's front hooves and the Umbrum whips them down to its sides and sits for a moment. It then turns to the shadow guard to its right and speaks with a male voice]
Umbrum possessed Princess Celestia: Akodu. [turns to the other one to its left] Mikenopa.
[The Umbrum then moves Princess Celestia's hooves straight out to its sides and the two shadow guards grab its new hooves and help the Umbrum get up from the chair and the Umbrum in Celestia's body gets down from the chair and the shadow guards let go of its hooves. The shadow leader leaves the control area for the claw while the Umbrum walks out with the two shadow guards, ready to begin its new life in its new self]
[Ryan looks around]
[Ryan sees no one and sees it's safe]
[Ryan comes out of hiding]
Ryan F-Freeman: The Umbrums must be stopped. No matter the cost.
[Ryan goes to the vat and sees a lot of female protoplasms]
[Ryan hears someone]
Princess Luna's protoplasm: Ryan! Ryan!
[Ryan looks into the vat and sees Princess Luna's protoplasm]
Princess Luna's protoplasm: Ryan!
Ryan F-Freeman: Princess Luna. I'll save you.
[Ryan grabs Luna]
Princess Luna's protoplasm: Oh thanks, Ryan. Now let me go so I can return to my body.
[Ryan tosses Luna and she flies]
[Princess Luna's Umbrum possessed body prepares to walk into a mansion]
[Princess Luna's protoplasm spots her body]
Princess Luna's protoplasm: Here we go!
[Princess Luna's protoplasm re-enters her body and Princess Luna falls]
[Luna's neck glows purple and an Umbrum comes out of her body]
[The Umbrum roars]
[Princess Luna gasps]
[The Umbrum prepares to attack when it sees it's out in the sun and explodes]
[Princess Luna sighs]
[Back at the cavern, Ryan sees Twilight's protoplasm and picks it up]
Ryan F-Freeman: Twilight. Thank Primus, you're okay.
Twilight Sparkle's protoplasm: Yeah. I miss you.
Ryan F-Freeman: Twilight, you're a protoplasmic head.
Twilight Sparkle's protoplasm: I know. But I'm still the Princess.
[Ryan launches Twilight]
[Twilight's protoplasm flies around]
Twilight Sparkle's protoplasm: How do you fly this thing?
[We see Twilight going towards her body]
Twilight Sparkle's protoplasm: There it is!
[Twilight's protoplasm hits a door and spins out of control]
[Back at the cavern, Ryan sees Princess Celestia's protoplasm and picks it up]
Princess Celestia's protoplasm: Thank you, my student.
Ryan F-Freeman: It's okay. Ready for launch?
Princess Celestia's protoplasm: Yes.
[Ryan tosses Celestia and she flies off]
[Ryan then sees the relic and takes it]
[Meanwhile, Princess Luna goes into the mansion and looks outside to see a protoplasm coming and goes into the mansion and sees the Umbrum possessed Princess Celestia]
Princess Luna: Oh. Uh... Hey, you!
[The Umbrum possessed Princess Celestia walks over to Luna and Luna shoves her in a room as the protoplasm enters the room]
Umbrum possessed Princess Celestia: You are needed.
[The protoplasm enters Princess Celestia's body and Celestia falls into a chair and Celestia starts moving as the Umbrum is about to be expelled from her body]
[Princess Luna gasps]
[Luna then sees what is happening]
[Celestia's neck glows purple and the Umbrum comes out out of her body]
[The Umbrum roars]
[Princess Celestia gasps]
[The Umbrum growls and approaches Celestia]
[Celestia gasps in shock]
Princess Luna: You could use a little sunlight.
[Princess Luna shines a light]
[The Umbrum explodes]
Princess Luna: That's one thing solved. The Umbrums must need our bodies to survive in sunlight.
Princess Luna: Like a how vampire needs to stay in the shadows. But what they are doing here, we need to find out.
[Celestia nods again]
Princess Luna: Are you ok, Tia?
Princess Celestia: (with Twilight's voice) Yes. But I'm not Celestia.
Princess Luna: Twilight?
[Meanwhile, Princess Celestia's protoplasm goes into Twilight's body]
[Back with Princess Luna and Twilight in Celestia's body]