Natasha Romanoff adopts Luna Lovegood.
I DO NOT OWN HARRY POTTER OR MARVEL!
One month after graduating from Hogwarts, Luna gets abducted by Hydra, not before killing her Dad, Xenophilius. They bring her back to base and experiment on her and torture her for 3 months trying to bend her will and break her innocence... they fail to change her mentality but succeed in making her magic far stronger. Seeing their failure to stamp-out her innocence nor her will.
they decide to try again later, and threw Luna in cryogenic freezing.
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2014: 1 month after the events of Captain America Winter Soldier.
While cleaning out the remnants of Hydra, Natasha finds a freezing chamber where she sees Luna Lovegood, even frozen she can feel the immense power radiating from her cold lifeless body. After feeling that much power Natasha knows that girl would have to go to S.H.I.E.L.D. or the Avengers, so in a rash decision, she vowed to never leave her side and have her live with her if the girl would agree.
After bringing home a freshly thawed and cold Luna to the Avengers tower they find out she is underage, barely, so Natasha steps in and asks if Luna would like for her to adopt her, And Luna says yes.
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Eventual LunaXWanda please.
The rest is up to you!