Blade Maelstrom Ability is the special ability for the Tack Shooter. The ability "covers the area in an unstoppable storm of blades". Basically, the Tack Shooter shoots a several blades in a spiralling shape in two directions over a few seconds. To get this ability, you need the Blade Maelstrom upgrade (Final upgrade of path 2). It deals good damage if the ability is used nearby MOABs.