Activate Monster Reborn lol.
This scenario is too good to let die, it’s just a shame op is anonymous.
Just how would 2 monster girls combine together into one body? While it’s not specified, I thought it would be interesting to go over the few ideas I had about how this would look. The first is a potentially gruesome appearance that could make the resulting monster look far more monstrous than intended. Take the 2 monsters and stick them together, the point of contact being a vertical boundary that runs from head to toe. Imagine i.e. a hellhound-harpie (hellharpie) combo, where one side is the furry hellhound, while the other is the more petit harpy half. Either way, she looks kind of silly and probably can’t fly. Definitely an anatomical challenge with combining monsters that are vastly different in size, proportions, or body type.
The second, and my favorite, is that a lot of monsters are half human and the other half being a monster, so there are plenty of combos where you can fuse the 2 monsters with a horizontal point of contact. Any kind of snake girl automatically grants her respective snake tail to the resulting monster. Any winged monster probably grants the top half with the wings. There are also plenty of monsters that have huge lower halves that might just be big enough to accommodate an entirely second half of a monster girl without looking really strange. Any sort of alraune combination results in the second monster girl sitting in the flower like a strange liliraune (possibly fused to the flower like the alraune). I think you could combine certain species (spiders, centaur-like beastman, kraken, etc) or other monsters with large lower bodies with other monsters so that both of their upper bodies are attached to the same lower half.
The last idea I have is that many monster girls could combine to make one body that has the composition of another monster. Any slime type monster combination results in the non-slime monster girl maintaining her appearance and features, but being composed entirely of slime (whatever member of the slime family it was). A ghost combination probably results in a floating, transparent form of that monster girl. Other examples include the lava golem, dorome, and ittan-momen.
What about the monster girls’ consciences? As far as I can tell, the point of the potion is to combine 2 specific monsters with each of their personalities, into one body. Well, any monster that maintains 2 separate bodies, like the alraune example, is pretty easy. 2 bodies, each with their own brain and everything else that made them who they are. But how about the monsters that are one body? Well, either they can both talk and think at the same time and have to figure out how to communicate, or only one of them can speak at a time and they again, have to figure out how to communicate. Lastly, some of the less intelligent/less individually minded monster girls might have an effect on the smarter monster girl. A zombie combination might just result in a more slow witted, undead monster. The reason I wanted to explore all of these possibilities was because the whole idea of this potion is that it’s supposed to take 2 monster girls, and combine them into one body that retains the best or most important qualities of those 2 monster girls. And that’s where I started to get real interested.