So.... just imagine... a Darkin weapon... being thrown into the void... what might happen? Do we get a Void Darkin hybrid? Or what would happen? And wouldn't that be an awesome champ concept? Just think about it... a Darkin with both Void and Darkin powers
No. Too much clusterfuck is bad.
I am eagerly awaiting the release of a void darkin demon female yordle noxian defector black rose kinkou order undead Aspect hextech-augmented champ who is also Kassadin's daughter and identifies as a Frozen Watcher.
EDIT: Okay real talk there are no humanoids born in the Void and Darkin weapons are meant to be wielded by humanoids. Further Voidborn intelligence is very much unlike human and Darkin so I'm not sure how the entire corruption mechanic would work out.
I dont think that that a Darkin posessing a Voidborn could actually exist, as the Void makes no prisioners, they just eat them, and I doubt a trapped Darkin could avoid being digested by the likes of 
A Darkin sorcerer though, using Void magic, similar to 
but way stronger would be really interesting, and I feel that possibly would be fit for them. Darkin got defeated by powerful mages, so they way to win back would be using magic nullfying materials like petricite, or using anti-magic, like the Void, also, we know that magic isn't strange among Darkin, as they gave Runeterra the Blood magic
I don't think it really works like that. With the Darkin, I'm pretty sure they trasmute the flesh to fit there own needs. The magical properties stay, but the flesh is re-purposed.
I could see a Voidborn creature or Void-touched organism coming into contact with a Darkin weapon, but I doubt they would have the willpower to overcome the Darkin. At that point it would be a Darkin using whatever flesh has to recreate a body that had a connection to the Void, but the physical properties, that Voidborn creatures use as they're main form of attack, would no longer be useful.
Now a Void-touched person who gained specific magical power from the Void and then the Darkin posessed them to make use of that magic, it could happen, but considering they are in 2 different design spaces, I don't think we will be seeing a merger of the two outside of skins.
I do admit though, that would be EPIC!!!
The Juh'Zan, the Ascended Darkin Aspect of the Void hahahah
Things I can say quite confidently about the Void:
They assimilate biological matter.
They enhance/warp ambient magic.
They 'eat' souls, as seen in Rek's flavor story with that poor kid. Soul ripped out and corrupted to help build Rek's Void tunnel.
At least one of them (we'll call it the Intelligence) is able to crush the will of other beings and subsume them into its own purpose. We saw that with Malz and Nami's fishy friend.
All those things in mind, a Darkin weapon cast into the Void would probably get gobbled up just as surely as any other living thing. The Darkin are powerful, sure, but the Void on its own turf is inexorable.
