[Autumn]

Correct me if I'm wrong but I think battlefields and houses spawn in the same area or at least the same Z Level, since houses don't load until someone enters it, its very possible that a battle had occured before someone spawned the house, and it spawned the house over top of the already used battlefield.

A long time ago, we had been bug testing and it turns out that if you fled while your movement grid was still up (not possible anymore, this was patched out) you could keep your camera centered on the old battlefield while being out of the battle, while doing this we figured out that houses could also spawn on top of the old battlefield and overwrite it.

Now the sword spinning in the gif is obviously Kinu's sword from her special roundtrip combo that forms the dark cinders, from what I know that animation doesn't stop through the whole fight, is it possible that the house spawned on top of the old battle field but it never erased Kinu's spinning sword?

I wanna note out that the sword has appeared in the arena before too, and random battles, but the explanation for those would be the same as the housing thing.