Certain names got dropped or hinted to in this show that have villian potential within them as well as current faces and they are:
The person that cursed the gemini coven
The person who killed cleos sisters
Mg and kalebs sires
Malivores children
The person who has prevented malivore from getting out and who sent necromancer back(they might not be a helping hand to the salvatore school as we think)
Triad again(what would they bring differently to the table this time)
Dark josie and dark alaric (what would they bring differently)
And then certain students- lizzie, ripper mg and flip switched tribrid hope
Im not going to put people who are somewhat on neutral like aurora or a past villian like katherine and kai, those are dead horses I no longer wish to entertain the idea of a return and I see no way a monster besides malivore would be a side villian cause that is the point of motw to make these monsters have their 1 episode of fame and onto another and so forth, its going to be vampires, werewolves, witches and humans as the villians if I had to guess to work alongside malivore.