A friend of mine asked about SCP and OCs over discord, specifically their designation, and said I had to do all of them. Though I did give the answer there, I decided I should probably compile it here and share it. Though after the fact I've been on tumblr to see that's been passed around a little with other people so maybe that's where they got it from. ANYWAY. This is going to be reaaaaaally long, additionally with the designations being explained as things go on as well as the process of elimination. So I'll be putting it under the cut here so it doesn't get too long.
So there's a lot of designations in SCPs and such, most of what you'll normally have to worry about is Safe, Euclid and Keter, there ARE secondary classes. By default any living being is at minimum Euclid because you cannot leave them in a room/box indefinitely with them not making decisions that you may not be able to predict/potentially dying from starvation and other things.
Secondary classes are Different and VERY hard to get things into. Because their containment usually is "literally physically impossible to keep their anomalous effects in a room" due to their nature. Either they are literally too big to fit in a containment zone, in outer space, or they are a phenomena. As an example of a phenomena, it would be the concept of flame itself as it would not be able to be contained in any way shape or form, and thus all you can do is keep an eye on it or take the afflicted.
So most of mine i know for sure would be in primary designation with three potential exceptions. Additionally none of mine could be neutralized, as that would be removing the anomalous affects from them, which in this case is flame itself. which could be done by killing them or other sorts of things but the foundations primary goals are: secure contain protect.
They do not do this on purpose unless they MUST and in most cases it would not be a must. Additionally even if some of them are not doing anything at the moment and effects of their existence is still happening, they still count as anomalous so people like Kira. She needs to be elaborated on by a LOT.
Note: Thaumiel is a very very tricky classification that I'll be avoiding. There has been cases where one SCP has been used to contain others, but in most cases this has to be determined to not be a threat to the thaumiel scp(as in will not result in their destruction) and they need to be a reliable way to keep the designated SCP IN the facility. As such while OCs like Osmio and Mercurio are very attached to each other and would search each other out, neither would really PREVENT the other from escaping after, and would end up taken by the other out. Thus is NOT a reliable way of keeping them in the facility. Because of this i cannot safely say any of mine would count unless they'd actively FIGHT leaving as well.
Next, Keter and Euclid are not determined by danger but how likely they are to escape and how hard to contain they are. it's ALL about containment.
So while I may place other OCs in Keter Vs Euclid, that's not because they're less dangerous than the others(some of the Keter ones are actually weaker than the others it's just the want to escape and the means they're able to)
Either way by looking over, here's the quick run down of what's going on:
Euclid: 6 designated - Bianco, Caladrius, Ragno, Silen, Smilodonte, and Vittorio
Keter: 4 designated - Mercurio, Osmio, Nascosta, Gambetto
Potential Apollyon(Otherwise Keter): Kira
Uncontained(Potential Archon[Otherwise Keter]): Presagio
Now I'll go more in depth of each specific OC by group.
Bianco - He is Euclid because he can very much be reasoned with to stay contained, he overall has qualms with fighting people for no reason, and generally refuses to do so unless they return with force. Due the SCP facility giving the SCPs what they want for good behaviour and being able to trust them(or at least the closest thing of trust) He would be able to be comfortable and wouldn't likely care too much after some time. Especially since they allow human scps to wander after some time as long as it's within the facility.
Caladrius - Though confident and strong, he only is confident in the Archives. The Facility is NOT the Archives, so it becomes cowardice and avoidance, he would pose little threat to escaping.
Ragno - As much as he would hold contempt for it, he doesn't care all that much. The man has depression already because of the position he is in, he wouldn't care enough to go back. Especially if he knows his family is safe. Which the facility would be able to give him proof of. He figures they can handle themselves better without him.
Silen - He minds his own fucking business constantly, you literally just place him anywhere and he keeps to himself. He pretty much just self contains but usually accidentally sneaks out not knowing that he's not supposed to leave at this time.
Smilodonte - He mostly fights due to his loyalty and since he can be reasoned with it shouldn't be hard for them to convince him that he needs to stay. He's pretty amicable so it's not hard, though he'd be a little fucking mad about the kidnapping.
Vittorio - He just wants to live a comfortable life, and boy is that pretty easy when you have an entire facility taking care of your needs. Sure there's chaos on the outside of your room on occasion, but what do you care? He never really had any people to be attached to, so he can make them here instead. The foundation staff have to deal with his flirting.
Mercurio - She is extremely difficult to contain mostly due to Osmio's experimentation on the both of them making her extremely resistant to being knocked out among other things. She has an intense amount of strength meaning containing her through normal means is difficult as she can blow a hole through a thick metal wall no problem. With her high aggression she would be very hard to keep in place and would try to escape very OFTEN. Sometimes succeeding for short periods.
Osmio - Much like his sister, He has all of the above, however him being a bit more fair tempered means he will not use force to escape unless required to. He will tamper with electronics and anything that he can see to free himself, and worse his ability to use many different flames at the same strength makes the above worse when he resorts to it. He tries to escape often, but at a certain point it becomes a game.
Nascosta - An illusionist who's main power is stealing people's faces and using her ability to analyze a person so very perfectly, that she'll be able to mimic them within a few hours of taking to them. Add to the fact they can just become invisible among other Illusionary tricks, it makes keeping track of him incredibly difficult and escapes extremely common. Fortunately it's mostly to fuck with staff but still.
Gambetto - Gambetto is a master thief and escape artist. Put him in any container and when he feels like it he'll be out in an hour or less. Though he himself is very friendly and chill, she hates staying in one place, especially one that she doesn't consider her home. So despite all that she is constantly being found escaped somewhere that she shouldn't be. They do not know how he does this.
Kira(potentially) - While her main body can technically be contained, her flame which she uses to essentially parasitize people into becoming her mindless monster puppets is practically impossible to contain. It can spread from host to host in a matter of quick little instances, and she does not even physically need to be there to do so. The SCP foundation taking her in would just be moving her main body from one container to another, as if you only counted her main body, she would be self containing as she never leaves her base for anything. She can count as a world ending threat as her main goal is to completely take over the human race and then turn everyone into monsters to ascend them from beyond human limitations. It is also not helped by her ability to essentially warp reality around her should she have enough flame just lets her leave any containment created for her.
I will also place Archon here, due to it forcing the foundation to give up
Presagio(Uncontained for sure, may be Archon after) - It is... Essentially unstoppable. As it has no specific weaknesses, excessively high regeneration to nigh immortality, extreme strength and speed, as well as damn elusive naturally. Capturing it is by all practical means, is impossible. Any containment you put it in may as well be a slight detour in its route for Presagio, and while not openly hostile unless you are back, it is simply not going to stay in place. Though they would not deem it 'best left uncontained' due to how it interferes with the world, which is why i was on the fence about saying it is currently an Archon.
Tyr - Well you see, he's just a man. Like as fucking terrifying as he can be, he's just some fucking guy. He doesn't have flame, sure he's pretty damn strong but that's because he trained himself to be, sure he feels otherworldly at times but once again that is practiced. This is just a man with a hand missing, gigantism and fangs. All of which can be explained by naturally occurring processes and thus he can't actually be designated as an SCP. So they'd just take him in thinking he was one because of greatly exaggerated reports, realize he's normal and make him a D class. (Note he fucking loves this, life and death and hyper specific rules he needs to follow? fuck yes.)