This is a monster lure and nailbomb. In coop mode, it attracts all monsters within a radius of 600 units and draws their fire. It sticks around for about 9 seconds then it explodes in a shower of spikes shot in
random directions.
The monsters can blow it up ahead of it's nine second fuse if they hack at it hard enough.
"IMPULSE 67" Shoots the ball.
It takes 40 nails. If you don't got em, you can't use it.
In deathmatch mode, it's just a 9-second grenade with a nail explosion.