Harry Potter x the Host
-A (female) harry ends up escaping the takeover by traveling far away, eventually she (due to exhaustion, and finding out everyone she knows[that still lived] are no longer themselves) is captured and becomes a host, but just like she fought of the imperious curse she fights her 'parasite'. She is able to keep her people a secret and her magic as well(the other magicals more or less committed mass suicide, since they couldn't stand the idea of being oppressed again, a few like harry remained but over time the fear got to them and their previous injuries as well, then forced harry to go and not return).
-Teddy may or may not have been with her (he would kind of take the role of Jamie from canon)
-harry ends up with Ian...Melanie and Jamie are there but Mel was never captured, they got away to the cave system with Jared before that could happen.
-which means harry is the one that Wanda ends up in...Or not
-harry fights done the 'possession' so roughly and totally that she destroys the 'parasite', of course this doesn't happen for a while since the change had to be made and harry had to 'recover'. Maybe a few days, so the parasite can think it has full control of for harry to realize what is happening, since she was put to 'sleep', and wakes up when they go to remove her scars, which were giving them trouble being magical wounds.
-so she suppresses her resident and destroys them kind of like a horcrux (Harry's power has grown over the years, and her magic doesn't like the idea of working for anyone but harry, so it helps harry fight back). There is a benefit to being a host even for a short while, besides the insertion mark on her neck, her eyes retain their glow/ring. Making it very easy for her to get around.
-when she realized she couldn't escape this time she hid Teddy(all she had left now) away and warded him in many protections(fidelious on a person), and with her magic protecting her mind, and occlumency therefore hiding all magic events(which includes Teddy's hiding place), they the parasites never find out about magic. Since all other magicals either died or have gone so far into hiding they will never be found again, and will probably pass away in their hiding holes. So the aliens never find out about magic, not even when muggleborns are born, since there is no more magic societies to teach them...harry made sure of this(along with her friends before they perished).
-harry then escapes going back to Teddy(somehow her magic physically expels the parasite without harming her, so it is truly only her inside her body again) the two of them then go off once more slightly easier this time(since harry now has the 'eyes' and doesn't have to pretend with her magic(Teddy uses his metamorphmagus skills). Harry uses a more advanced point me spell to find humans that are still themselves. This leads her to the caves, where on her way there she runs into Jeb and a few others, they 'capture' her not really believing her to be herself, but can tell she is different. Eventually she brings them around with her stories and magic.
-perhaps instead of finding the cave system so much later than the others she finds it near the beginning when they are only starting out, and she makes a friendship with Jeb, where she helps him get all he needs to start out, but can't stay since she has to make sure all 'magic' is destroyed or so far buried it will never resurface again, before it is found out, so she leaves and then comes back with the glowing eyes and Teddy.
-Ian after he comes around takes a real liking to her, though she is hesitant, and Teddy takes a liking to Ian, and it is eventually through Teddy that harry agrees to let Ian 'court' her, and they get together
-over the stories timeframe she helps them get 'alien' supplies, so they can live easier.
-not sure whether or not Burns will come in or not...since not much is known about him and his humans