First off, Howdy!

So, I've reached the point in my story where I need to write more animals/creatures for my main character to face. I've already used many of the animals in the lore, but since my story is moving to a new northern setting I feel like the creatures would be out of place. I already have an idea for wolves and manticores being built more like a Demons, from the Metro series, but besides that I have nothing. I really want to create new beasts, but I'm a little afraid of not staying true to the universe's rules. Any suggestions on how to proceed with this?

Thanks!

7327635

manticores being built more like a Demons, from the Metro

Aren't manticores already as hardcore as they could be? Because with one we see in canon being "just a baby" I assume that rare adult manticore is the horror as big as the house.

Anyway, creating any creatures you shouldn't look for any inconvenience universe rules. You just need to ask yourself "why it haven't spread all over wasteland, pushing everything else to extinction".

Like I created Hellhound alternative for zebra lands, which is really big and really smart jungle kitty, big and strong enough to maul tank. And I explained why exactly they haven't spread all over the land by hating magical radiation, so they just have no reason to invade Equestrian Wasteland and nearby countries. Also, they haven't exterminated other things because, like deathclaws from Fallout 2 they are smart and peaceful enough to refrain from genocide.

7327635
Winona.

That's an easy one. Creatures in the show are a mix of mythological and original, fictitious beasts. Look into creatures of ancient myth and put a fantastical spin on them, and remember that Balefire is necromantic in nature. Undying mutations of everyday animals are fair game.

In my fic, I made up "storm nagas," flying serpents with six eyes that spit ice loogies and like to harass anything that encroaches on their territory. The younglings are a meter or two long, and a brood mother can be the length of a freight car. The "ice" they spit is a gland-produced, refrigerant-like venom that expands and freezes a second or so after it leaves the naga's mouth, solidifying into a hard shell to immobilize the prey. The prey, ideally a bird or small land animal, would be left to freeze as the venom leeches body heat away, since it has a specific heat an order of magnitude higher than water.

I like to take inspiration from Final Fantasy games, as well. They have a wealth of interesting creature designs.

7327635 Dude, go freakin' wild. Whatever creatures you want to make do it, just try to stick with the mutated animal theme. If you haven't done bears or yao gui or whatever, that's always an option. Perhaps they're bigger and meaner in the colder north. Maybe moose as well (and, if that makes you laugh you've never seen what a normal moose can do) with vicious bone growth sprouting from their bodies.

7327635
Weren't manticores immune to taint or something like that? I'm almost sure they couldn't mutate. It also depends on what theme the "new northern setting" has and how far north are you going.

7327736
When I mean a northern setting, I mean we're heading to Stalliongrad which in my personal opinion is just frozen wasteland. I feel like there's enough distance to have some crazy creatures. Also if that doesn't work I could just use my biological megaspell as an excuse for mutations, right?

7327728
Moose...I like that idea. Don't mind me. I'm just gonna take it slowly back with me.

7327663
This is some great information to help. Thanks!

7327654
I'll keep that question in mind. Thank you!

7327775
If it's just a frozen wasteland (as in only snow and ice) then there is no way for ponies to live there, because, you know, they can't grow food, and the ecosystem collapsed aside from maybe aquatic life, polar bears, and penguins. In any case, my only advice for you is to look up wildlife in the Russian tundra. There are some fun things with claws and fangs running around like tigers, snow panthers and cute arctic foxes...

7327635
The simplest way of coming up with new monsters might just be to look through the various critters in pre-apocalypse Equestria (The wiki even has a convenient list of creatures to look through). If they've got a good analogue in the other materials, even better.

For example, when I was writing about passing through a long stretch of swamps, I wanted some creatures there to make it a hazardous journey. Between cragadiles in MLP and deathclaws in Fallout (And especially gatorclaws as of Fallout 4), that led to the creation of the swampclaws in my own story. And MLP has a lot of critters, many of which had yet to appear in the show by the time Fallout: Equestria was written, so there's a lot to draw from.

Make sure to do some digging into the creature and see if they've got any existing in-setting information. Like Haunted Toaster said, manticores are explicitly noted as being immune to taint and radiation (Possibly due to their somewhat hybrid nature?), to the point that they're being used to research possible cures or preventative treatments. It's good to look up how they work in the setting already so that you don't get clashes with people's perception of the setting. Do be a little wary of solutions that seem somewhat contradictory to the setting while not technically contradicting it, because people are generally more likely to note the former than the latter, which makes me a little cautious of coming up with some alternate solution like a biological megaspell to explain mutation. That said, manticores being immune to taint and radiation is the kind of small detail that a lot of people might not remember, so you might get away with it... but I generally recommend against actions that can be described with "you might get away with it."
7327654

Aren't manticores already as hardcore as they could be? Because with one we see in canon being "just a baby" I assume that rare adult manticore is the horror as big as the house.

Are you sure you're not thinking of chimera or star spawn? Because I don't recall any suggestions that the various manticores Littlepip encountered were babies, but both the chimera and star spawn were described that way (Including Littlepip's surprise when it was revealed that the star spawn was "just a baby.")

Unless you mean "canon" as in the show, in which case we've seen several manticores, all fairly similar in size and appearance. Fluttershy called one a "little ol' baby kitten" when playing with and scritching it, but that's the kind of thing she does with full-grown animals; it was more about it being nice and friendly rather than young.

7328104

I kinda assumed that manticore encountered in Everfree was just a baby. Therefore adult manticore would be much bigger. Of course there is question why Littlepip never encountered adults... but eh, I just justify it with adult manticores being extremely rare encounters of "all witnesses are dead now" type.

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Metro part of the story. Folks are living underground.
Thanks for the extra information!

7328104
Okay, I see what you're saying. I'll be taking that advice to heart.

7328171
If it was just that one, maybe, but we've seen other manticores in the show that all appeared the same age, and it'd be pretty strange if they're all the exact same age of babies.

I mean, you could say that all of those (And all the ones that Littlepip encountered) were actually babies, but I'm not sure many people would buy it.

7327654

Aren't manticores already as hardcore as they could be? Because with one we see in canon being "just a baby" I assume that rare adult manticore is the horror as big as the house.

The manticores we see in the show have a mane. Lions only get that when they are adults.

The Star Beast in Boast Busters was revealed to only be an Ursa Minor, and not an Ursa Major, but nothing like that was ever said about manticores.

7327635
I have giant jumping spiders in my story. Given the fact jumping spiders are absolutely tiny; about as long as the width of a fingernail, the "giant" versions were about the size of a large housecat (and still absolutely adorable ). They were kept as guard animals and hunting companions by the local tribe of (non-mutated) Diamond Dogs, and were generally neutral to ponies, since (like the diamond dogs) they fed on the local radroach population.

So yea, sky's the limit. Take any animal and imagine how they'd fit into the local ecosystem.

I also introduced my own type of ghouls; the Ash Ghosts. They were the side effect of a megaspell based on phoenix fire, rather than balefire.