𝔀𝓱𝓮𝓻𝓮 𝓰𝓻𝓾𝓫 𝔂𝓪𝓹𝓼

I did a little looking around and both Kohlrabi and Shallot could make cool moroi / moroaică, which is a type of creature from Romanian folklore! Though there are certainly a lot of interpretations of it across time, a source I found says there are two versions, living moroi and dead moroi.

Living moroi are marked from birth and are believed to have two souls. When a person falls asleep, their other soul would escape from its body to cause torment, before returning to the body in the morning, with the main person unknowing of what they'd done.

Dead moroi are born from tumultuous / unfinished deaths. After their deaths, they rise again to feed on the lifeforce/energy of living beings: they're more of a patient, longstanding hunger. According to folklore, the two types of moroi are not actually distinct, but merely two different versions of the same beast– the source says "some people are wrong in a way death cannot cure" which I think has really interesting implications for Kohl and living Shallot both.

Them both being the same creature in different states would offer an explanation as to why they're sent out together (other than Melan wanting to see Kohl suffer). Since dead-Shallot recognizes Kohl as a fellow moroi she won't attack him (even since he's technically alive). I'm struggling to find any correspondence on whether living moroi have any abilities while awake, but I'm sure Melan could work a little magic to make it possible. Maybe he sleepwalks / gets put in a subconscious state to allow his other soul/powers to come through.

( https://godsandmonsters.info/moroi/ )

I think it makes more sense for Buttermilk to also not be undead (instead more of a witch or warlock, maybe even a necromancer?), though if you wanted to ascribe an undead creature to him he could make a fun draugr. Primary motivations that can draw a draugr from their grave are greed and envy, both of which Buttermilk displays. In the original Icelandic folklore they're known to be shapeshifters (so he can maintain his former human form) and possess powers beyond that of their mortal shells, including the ability to cast curses and also infect others with their curse. There's also a fun little tidbit about one of the primary ways to kill a draugr is by "breaking [their] posture," and Buttermilk is someone who has a sort of "posture" to him with his polite ways of speaking and general composure, though he has moments when it cracks. Integrating that into a way to put him to rest would be really interesting...

( https://en.wikipedia.org/wiki/Draugr , check primarily the "Icelandic sagas" portion)

As for Sundae, I think a doppelgänger (as in, the actual creature-archetype from which the colloquial using is related– apparently associating the term with the creature came much later!) works best. She's still kind of Sundae, even under Melan's control, so putting her as a kind of "evil double" I think makes the most sense. Maybe Melan, instead of taking Sundae's memories and leaving her a husk, took Sundae's ka (or spirit double) instead and that's who she takes as a minion, leaving Sundae alive and mostly whole but stripped of her powers, maybe?

( https://en.wikipedia.org/wiki/Doppelg%C3%A4nger )