The Mother (Doctor Who)

First of all, she is an overpowered godly character from the same universe as the Toymaker: she's meant for both emotional mother-doctor threads AND comic relief, because she's simultaneously the type of character who could sneeze this universe out of existence and an embarrassing mom who doesn't get her son's hobbies but will bring him tea while he plays. 

If you know you are someone who will not be having a laugh writing with a slightly judgy god that cannot be killed, this isn't the AU for you! (I get it!!!). This is supposed to be funny other than emotional, but if you are bothered when your muses aren't taken seriously, avoid her! 

In her first thread she called the TARDIS her kid's squeaky toy because it makes noise and it's a little happy machine he carries around, and she means well, so that's the level of 'superior being' we are speaking of.

That said: merely being in this universe and adapting to it, including having a humanoid form, will limit her powers and force her to accept some laws of physics, otherwise she'd fix everything that happens ever and there will be no more plots to be had; plus, from her pov, her son is 'doing his thing' and a mother would not take the gamepad to win her son's Call of Duty campaign, would she? She'd let him play the way he wants. 

(The 'I don't get why my child likes Pokemon but I'll say all the ooohhh and wooow necessary to make him feel validated' type of mom.) 

Gender and orientation: She'd accept the pronouns she/they and maybe even he, she doesn't have a specific gender besides 'I carried my baby and I'm in charge', but I'll use "she" to keep it short and clear. She may also identify as 'female/woman' when with humans since she can see that as the closest to her own, or 'genderless' outside of it. She's capable of growing attachment but giving how she sees everyone as her kid, her kid's friendly pets and her kids' enemies, so shipping isn't exactly easy, so demi-aro and ace but sex favorable. 

Past: Her name, much like everything in her native language, would burn this universe upon contact, so she has 'no name' apart from whatever the Doctor may give her, but she'll pick 'The Mother' as title, since that's what seems closest to explain their relationship in his language. This is also so that I don't decide the Doctor's previous name and other details like that.
When she was a young Unspeakable Horror she got pregnant from a "lower being" while celebrating a victory (she fancies herself as more of a traveler than a warrior. she's a warrior), and the "lower being" in question could not accept that he would not be allowed to lead by her side even after fathering her child; she chose to raise the baby on her own, a teen mother of only a few thousand years but he waged war, which created a crack in the universe's edge, and out of revenge threw the child inside. The Mother ripped him apart and ate his essence, a way to end the war and his existence, but promised payback to his co-conspirators before trying to force her way out and into this universe. From her pov, it took her 500 years, while it was clearly far more for the child who became the Doctor.

To be clear, *she* was detached and weird by her own race's standards too, but having her baby made her finally care for someone and brought her empathy that she was missing before. Normally in their race there are severe and distant parents but a good social-net of comrades: she was asocial but became a cuddly mother (perhaps exactly because looking for the missing connection).

Now: All she cares for is to reach her child, the one being in the universe she truly loves, even if it means tearing universes apart or, worse, being asked not to hurt people indiscriminately by the Doctor. She has many forms but she chose the partly blue one to blend in/communicate; she sort of self-translates herself like the TARDIS, can open portals, can look through minds when searching for her kid (and casually burn them if not careful) and can, obviously, wipe away entire armies with a nudge, but she's holding back for her son, can fully look human if required, and will NOT be looking into anyone's mind when she can just talk. She will also feel 'her kid's presence and other beings from her universe.

I will assume she's met the Doctor if someone else wants to interact with her, to prevent death and unwanted mind-reading, she's already trying to adapt to what her son would want her to do. Your muse can feel they are in the presence of some creature they are meant to fear if you want.  

The Doctor is her everything, he'll always be her baby, and he can do no wrong in her mind, unlike anyone who attempts to hurt her when she can see it (in which case the Doctor may have to step in or that person will be scattered through the universe). She does like humanity and human children because the kids look exactly like their race. She'll find this universe more interesting once she stops looking down on it.