This is the second time i've seen this item (thing) since the update.
The first time, a few days ago, i saw it drop from a zombie/bot during GiM. I was pretty sure it was a drop, but after a while, i started to doubt myself and came to think it was simply part of the decor I had never noticed before.
http://oi40.tinypic.com/2cdy0kz.jpg
Well it dropped again, this time from a box, on a different level.
http://oi41.tinypic.com/1416yoi.jpg
I tried picking it up, but had no luck and then i accidentally closed out my game window (thinking it was the screenshot I had just taken), so i hope i didn't miss out on a unique item.
Has anyone else seen one? Did i miss the memo?
It's an Artillery Strike, one of the new usable items recently added. If you have a free slot open in your vials hotbar, you can pick it up and use it. It'll do a series of explosions randomly scattered around the spot you were standing when you activated it. The explosions do a pretty nice amount of damage actually, but it works best when you have some method of holding the enemies in the area (like a Shivermist or Vortex Bomb).
EDIT**
This is the patch that added it (Oct 16)
http://forums.spiralknights.com/en/node/91052