Soulmate Natasha romanoff X (Invisible)and(Mute) OFC.
I do not Own Marvel or any of their characters.
This story starts with a mute girl who was taken bye Hydra as a baby and experimented on as a test Guinea pig which causes her to be invisible permanently but they failed in a way where she can only be seen by her soulmate who unknowingly to everyone is Natasha Romanoff.
Then 20-ish years of experimentation which involved painful injections, taking apart and putting back and putting back together (with no sedatives), starvation, and much more.
Now, horrified, starved, and on the brink of insanity, what will happen when the Avengers break into the facility to stop Hydra from doing illegal human experimentation...After beating them, they are packing up when the Black Widow sees something that nobody else sees.
P.S. Make it romance and lots of angst please.