Well.

That's interesting. 

Isotte-in-the-bugacorn trots towards their shared room. 

Someone seems to have taken control of her body.

Can she still use her magic? No. Can she alter her illusion? No.

None of her friends are here, which rules out what would otherwise be her next option. By the time she's able to go back home, she will probably have been subjected to further mind control and won't want to be rescued.

Fuck.

Hopefully someone is reading her mind. She will think about how, if someone were to rescue her, she would try to repay the favor.

Isotte trots into their room and looks around. Something she could use to restrain this body that her roommate couldn't immediately get out of as soon as Isotte steps out again would be ideal, but she's prepared to get creative. 

Isotte's roommate's possessions and furniture generally suggest a world that's lower-tech than the Ghost Zone. On part of her floor is a rubber mat. On her desk are photos that appear to show several ponies with various levels of hornedness, wingedness, and technicolorness. The photos give no indication as to whether these ponies are also secretly bugs.

Probably the most surprising of the unicorn's possessions is a padded floor mat. Among the objects which could most conceivably be repurposed for restraint are a wooden bed and a guitar with wire strings. But there are also several locked boxes.

Yeah, no, Isotte is a musician, she's not going to potentially wreck someone else's strings by using them as restraints. Her own bed is a four-poster with a canopy which, critically, has sashes; she can use those. 

Once the quadruped is bound, Isotte leaves her body and materializes in front of her.

"I am sorry for the inconvenience, if it matters."

There is a flash of green energy from the bugicorn's horn to Isotte, then intense pain, heat, electric shock, and being thrown backwards.

OW.

She slides down the wall to the floor, then staggers to her feet--she has to be ready to dodge, if her roommate does that again--is she untying herself--

Yes.

She lunges for her with more bed sashes.

Everything becomes green-tinged, and moving becomes difficult.

The knot-untying aura vanishes.

(And now Gossamer needs to try to untie these knots while also holding a second, heavier object. And to do this before she runs out of energy. Or her roommate comes up with some other trick.)

If this is effortful for the bugicorn, no sign of this is immediately visible.

(it's pretty effortful, but illusion-coated changelings have very good poker faces.)

Okay does the green-tinged slowification thing keep affecting her if she goes intangible, either one seems plausible.

Not instantly, but it quickly fades out.

She overshadows the quadruped again and tries to add more restraints. 

In spite of its appearance, the quadruped's body is a lot tireder than it was before. It's also feeling something like hunger, but for something that's not food in a place that's not the gut.

Huh. Interesting. 

She leaves again, appearing in front of them. 

"Thanks for the apology. What do you want from me?"

"Oh! I'm going to sing to you."

The unicorn sighs.

(Under the illusion, so does the changeling. This is probably going to be mind-control. But it's possible her roommate just really wants an audience for her song.)

"I'm afraid I don't have time to listen to you sing at the moment. It's looking like I need to learn some new magic before I can safely eat here, and I want to figure that out as soon as possible."

"Don't worry, it won't take long." 

"Well, knowing where we are and how you're going about this, I'm also worried the song might be a mind-control mechanism. And I'd much rather activate the death wards than let you use me against my friends or my people."

"What? I have no reason to do that."

"Some ponies would want to use me to enslave them, or to conquer Equestria."

"Do those ponies have access to all the worlds this place touches?" she sweeps out an arm. "Even if I decide I want to conquer someplace, I'd rather pick somewhere more similar to what I'm used to." 

The ghost might be lying, of course. And she might actually be able to kill herself.

And then she might be able to find a love spell that she can cast on someone invisible and insubstantial, and probably that would keep Isotte from enslaving her or her friends.

And she'd rather not be enslaved herself either.

And the ghost might be telling the truth, and she might not be able to kill herself or find a spell that's adequate.

"If you swear to leave my friends and my people be, I will listen to you sing."

She nods firmly. "I swear to leave your entire homeworld alone, except insofar as you ask me for help with something or of your own, non-mind-controlled will, choose to release me of this vow."

"Thank you."

She shows the mix of relief and fear she's feeling on the illusion. Its ears stay pointed at her roommate. The aura on her horn and the corresponding one where she was untying the knots vanish.

(Isotte not being familiar with horse body language, some of this will probably be lost on her)

And Isotte begins singing. 

It's beautiful.

It really is; there is mind control in the music, but it's just making Gossamer adore her and want to make her happy, not affecting her opinion of the singing itself. 

Gossamer will try to join in with some improvised lines about how cool Isotte is and how much she likes her.

(Gossamer is also a pretty good singer, and by the standards of most worlds is very good at improvising lyrics.)