The item isn't new, it came out in Smash 4. Though its game of origin was Kid Icarus: Uprising. I kept thinking Zelda: Skyward Sword. Shows you how well my memory of both of those games really is huh?
In Smash Bros. you pick it up and you can throw it or drop it where you like to.
Once you do it sends laser orbs in one direction. You can strike it to make it change direction if it isn't going the right way.
It isn't my favorite weapon in the series or the game, but I liked it. It's not overly powerful, it can be avoided, and has some decent balance. But getting hit by one isn't a good idea. It does pack a punch if you're not careful.