how to solve big empty room

[Disco Battle]

i cant help but to notice the vast rooms of empty and when i aquired the wing upgrade to fly over it there was things on the other side i.e. arcane powder to which the kind lady informed me of which i must extract five components of the bullet to kill the past (including the arcane power) which i presume are due to big ol' rooms, and they are

tl;dr what do with empty rooms?

[Danmit]

Hard to parce what you're saying. Try some punctuation next time - I'm not just being a pedant, it is seriously confusing to have a run-on this long. Anyway, if you mean that big empty room in particular, you've grasped the purpose: to get the Arcane Gunpowder. You need to bring the powder to The Blacksmith so that she can use it to make the Bullet That Can Kill the Past. Flight is one way to do it, but you can get across without it - the minecarts in that room are on invisible rails.

[Danmit]

There aren't a lot of empty rooms - the only other ones that immediately come to mind are secret floor-related rooms on floors 1 and 2 and another Bullet That Can Kill the Past-related room in floor 4. Looking back at your post, I think you probably were talking about this one anyway. Lage empty room with nothing but spikes? Flight is super convenient, but it's not necessary. There's an invisible path across, referencing Indiana Jones and the Last Crusade. Use the empty casings from reloading your weapon to find the path. If they don't fall into the pit, there's path there. If you happen to have a weapon that sprays any sort of water or goop, that's a much faster way to reveal the path.