AUTHOR'S NOTE;;
Ok I'm gonna get all these OCs done and dusted and get back to work on other stuff. I'm currently just settling back into an outside story at home, which I want to get at least partially through by the end of the Christmas holidays.
This character was submitted by lagiacrus123; thank you! I hope you find this review useful.
- Siri Mom.

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BASIC DETAILS;;
------ Name: Frostfire.
I'm going to stop you right there.
Really? Frostfire?
First thing's first: how many IceWings have you met with two-word names? There's only a handful. What about SkyWings?
None.
Frost could work as an IceWing name, and Fire could work as a SkyWing name. So, I suppose you do have a fair point in combining them. But... really? It just makes your character seem... sloppy. This name is overused in the fandom and also pretty uncreative.
I believe that you as a writer have the capacity to think of a name that's a bit more unique than this.

------ Age: 18.
*shrug*

------ Gender: Male.
Good good.

------ Sexuality: Bisexual.
Loving the LGBT+ I'm seeing everywhere here.

------ Tribe: IceWing/SkyWing hybrid.
*sighs*
do you have any idea how unlikely this hybrid is?
The two tribes have been at war for the past 20 years, by all the snakes! It's highly unlikely an IceWing - especially a rigid dragon who cares about their rank - would abandon their post for a SkyWing without some real convincing.
But I suppose you can't really change this, since it does compose a significant part of your dragon's persona. But... maybe avoid this in the future.
Also we have too many hybrids in the fandom.

------ Abilities: he is able to withstand cold temperatures but is not completely immune to it.
Good good.

He also can fly faster and farther than most dragons but couldn't out fly a pure blood SkyWing unless he had a fairly good head start.
NICE.

He can't breathe fire or ice; only smoke. His fighting ability is lacking.
Holy moons this is fantastic !!!

His greatest strength relies in his amazing memory and quick learning abilities.
This too. You've captured this hybrid perfectly, and given him some perfectly balanced physical abilities... along with a wonderful trait of his own; one that isn't affected by his tribe. Good job here!

Relationship Status: Single but has a crush on a MudWing named Mudball.
Awwwwwwwwwwwwwww. Mudball is such a cute name, too!

------ Occupation: None except for the occasional odd job he does for his friends.
So... he has no job? Dang. Must be either very wealthy or very poor; I'm assuming the latter, since there is no way a hybrid of his sort would ever become rich under any circumstance.

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PHYSICAL DESCRIPTION;;
He is an orangish red with blue streaks going through the orange which can make a very bright flash of light if the sun hits them just right.
While I doubt this would actually occur in a hybrid - generally, the dragonet will inherit their mother's colour predominantly, with a few tinges of the father's colour - you've included a lot of detail, which I like. So, I'll leave it be.

His eyes are a blueish green like a seafoam or teal color.
Once again, nice detail.

He has two sets of scars one on his right side and one on his left because of his parents.
Oh three moons.
I'd like to know more about said parents later on.

He is short and very thin.
Good good.

He has the IceWing mane of horns and the horns on his tail. His horns are a blueish tint and at the tips they are a dark blue.
Very descriptive! I'm assuming his mother is the IceWing, then? Since, as I've said, hybrids in the canon mostly inherit their mother's characteristics.

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PERSONALITY;;
He is very shy at first and almost always develops a stutter when he talks around dragons he's never met. He's very submissive and will always try to talk his way out of a fight.
That's not really like an IceWing, but I'm glad you put this in. You've been very detailed in your descriptions, and you've delivered a very clear character concept in these two sentences alone. Great job!

He always tries to look on the bright side of things and is very kind and mature.
I'd marry him.

He believes that he's not very smart but he is actually quite smart and has a knack for thinking up good strategies or plans which has led his friends to make him the deciding vote in almost any situation.
This was good, but the whole idea of "I don't think I'm good at this thing but really I'm brilliant it" is way. Too. Common. Surely if his friends always relied on him for planning he'd have some inkling he's good at it?
Instead of saying "he doesn't think he's good at things", you could maybe change it to "he doesn't think he's good enough at these things". That gives us the impression that he knows he's good, but is still humble and still wants to improve. Which is a lot better than the insecure, almost whiny image I'm seeing here.
Just something for you to think about, really.

He is open-minded and will accept new ideas with open talons but he will argue a point across if he feels there is no other way to explain something. He is also usually very quiet and doesn't talk in a conversation unless asked to or if he feels that he needs to.
Perfect!
I can imagine this character very clearly. Great job in this.

His major flaw is how he is always putting himself down and never believes in himself to be as good as he could be.
No. Right there. No.
As tempting as it may be, this personality trait needs to stop. It's very annoying to RP with, and makes it sound like you're:
a) Looking for attention. Or your OC is, because he's constantly putting himself down.
b) Too lazy to develop a proper flaw, or unwilling to make your precious baby too imperfect.
You've got a great personality here. You really do. In this case, though, I'd recommend either delving deeper into that insecurity - making it a major issue for him - or altering it.

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BACKSTORY;;
He was abandoned as an egg by his father and was alone for the majority of his life and had to teach himself to the best of his abilities to survive.
Wait... where was his mother?
Additionally, why did his father abandon him? We need a reason.
Finally, NO. A dragonet - especially one just hatched from the egg - would never be able to teach himself to survive. He'd need some sort of adult dragon or caretaker (even another animal) to look after him, at least for his first year or so alive. Remember, dragonets are small and vulnerable; there are many creatures that can and will easily (and happily) see helpless infant Frostfire as a tasty meal. And it's unlikely that he'd be able to defend himself. Either way, he wouldn't be able to get food; unless he ate berries. And if he did somehow manage to survive off these long-term, neither IceWings nor SkyWings are biologically-designed herbivores. It's likely that he'd be very undeveloped as a result, and incredibly feeble/weak.
Finally, there's illness, passing patrols and loneliness to deal with. He would end up sickly, weak, feral and probably unable to talk or behave like a civilised dragon.

After a few years alone he flew off determined on trying to find his parents and ended up in Possibility after seeing the town one night while flying where he was taken in by a kind elderly MudWing named Swamp Grass who took him in to raise as his own.
This is what I'd be focusing on. Immediately I'm saying take a few things out: trying to find his parents, for instance. If he wasn't raised by his parents and never saw them or any other dragons, it's unlikely he'd know what parents even are. He'd have some vague concept of loneliness - a little root instinct - but wouldn't really understand it. Definitely not enough to embark on a giant quest to find them.
However, I do like the idea of Swamp Grass. So I'd recommend changing it: instead of being abandoned and forced to raise himself, perhaps he could have been left as an egg in Possibility. Swamp Grass would find the little unhatched dragonet and raise him from the start; that takes out all the complications of a baby dragon unrealistically raising itself in the wild.

After a few years of living with Swamp Grass he convinced him to tell him what he could about what he was. After finding out he set off again to find his parents.
Take out the "again" and you're set to go.
I can imagine Frostbite would at some point be teased about being a hybrid; which would spurn him to ask Swamp Grass where he came from. So yes, this could happen.

He eventually found both -
I'm gonna stop you there. How did he find them? Where did he find them? How much time did he spend looking for them? You need to add more detail.
Also - both? You mentioned nothing about his mother in the start of his backstory. Did she agree with his father's choice to abandon his egg?
Which parent was the SkyWing and which parent was the IceWing, for the moons' sake?

- and they both told him he was a mistake that wasn't meant to happen. They proceeded to mark him with the scars he has, promising him if he ever came back to the IceWing or SkyWing kingdoms he would be killed.
Dang. Parents... don't do that.
You don't have to remove this, I suppose. But it really gives you some severe Mary Sue points. Remember, parents are possibly the biggest, most powerful influence in any child's life. Not having parents in the first place will likely have given Frostfire some temperamental issues already - or at least some insecurities. He'll also likely have built up a very complex daydream/image/fantasy about what his parents are like: and upon meeting them, this daydream is shattered. This will IMPACT HIM.
Another reminder - torture is no light matter. Just research testimonies of survivors; all of them are scarred mentally as well as physically. The trauma basically breaks their minds, and leaves them scarred for basically the rest of their life.
In addition to this, it's his parents torturing him. That would be more than likely to drag him over the edge; he'd become severely insecure, probably terrified/paranoid, and very depressed. For a long, long time. Probably the rest of his life, actually.
But you've showed none of that in his personality. You need to fix it.
Also, maybe add in some reasoning? Exactly why would his parents hurt him like that?

After all of this he developed his fear of strangers that he still suffers from. He still loves his parents but us deeply afraid of them as well as both of his tribes figuring they would be like his parents.
I...
While the fear of the other tribes is good, and the single remaining string of love for his parents is perfect, I really doubt that would be the only effect to hit this dragon. Unless you make the fear of strangers and his parents' tribes really intent - as in, he panics and flees every time he sees one - you need to consider adding some more, or removing the traumatic event altogether.

He eventually came across the MudWing, Mudball, and the RainWing, Boa, and developed a close friendship with both.
This is good... but what happened to Swamp Grass? I'd love to hear where he went.
Also, I like your choice in tribes. RainWings are viewed as one of the most nonthreatening tribes in Pyrrhia, and MudWings... well, since he was raised by one, I can imagine he'd trust them. I'd enjoy hearing about how their friendship developed, though.

He lives alone in the very same mountains he was born in where he makes maps of the surrounding area and offers them to anyone who may stumble across his home to keep them from getting lost and tries to help everyone in anyway he can.
Nice happy ending, there. I'll give you credit for that.

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COMMENTS;;
------ The good...
Overall, I actually quite liked this character. You gave him a very good personality, and didn't go overboard with his abilities. So yes, he would pass as a hybrid. But...

------ The bad...
Wow wow wow I'm really sorry. I am.
First thing's first, the name. I just think it's really uncreative. Why not branch out a bit? You say a MudWing raised him - so it's likely that the MudWing would name him a relatively MudWing name. Which would be quite amusing; also, MudWings have some very interesting names too - Hickory, Morass, Cienega, Rush (which also sounds SkyWing-y), for instance.
Secondly... backstory backstory BACKSTORY. It doesn't flow consistently with his personality, and is way too packed with trauma, tragedy and violence. Which would work well, I guess, if you'd actually had it reflect somewhere in his personality - but you haven't.

------ How you can improve!
I like this character, and I really do think he can be improved and eventually crafted into a 10/10. With a bit of name tweaking and thought to the description (which, by the way, was great - I loved the detail!), you can make him great.
MAKE HYBRIDS GREAT AGAIN. BUILD A WALL AND ENCLOSE PYRRHIA UNTIL THE MARY SUES OUTSIDE DIE OFF.
Okay, no more Trump jokes. If I just politically offended anyone, I'm sincerely sorry. I don't even mind him - I mean, I'm not pro-Trump, but I'm not anti-Trump. I'm not even American. This is an OC review so none of this matters -
(*ahem*)
You need to consider some things with your backstory. Firstly - take out the part about the dragonet raising himself. It's impossible - or, the chances of him surviving are so slim, it's barely even something I'd consider. I would personally change it to say that he was abandoned in Possibility, and rescued as an egg by Swamp Grass. It's more realistic and spares us a bit of tragedy and bleh.
Secondly, change the part about his parents. Is is really, really necessarily?
If you're going to keep the part about him being scarred, you need to mention somewhere in his personality that he's traumatised. Losing a parent can shatter a child; the parent turning on the child can cause the child some severe long-term mental complication, and would likely damage him for his entire life. So his ending wouldn't be quite so happy - more okayish.
I'd recommend taking out the part about his parents scarring him. Perhaps he finds them, and they tell him to go away. That'll be easier on you and him, and more realistic (wow I talk about realism a lot).
If you still really want him to be attacked, without the necessity of writing out all that complex emotional tanglework, I'd recommend saying a random patrol attacked him. Perhaps a group of IceWings or SkyWings (depending on the territory). You can still have them ask what he's doing - him tell them he's searching for his parents - them tell him it's hopeless, he's not meant to be, et cetera. He can leave in disappointment and fear, deciding that if all dragons are like that, he never wants to meet his parents.
Also, tell me where Swamp Grass went he sounds so nice.

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OVERALL RATING;; 4.5/10.
Great job in general, but... he does need some work. Read above ^^.

Thank you for submitting!

Wow this section just gets smaller with each review.

- Siri Mom.