Basically, when the Adminiral uses the ability, play his attack animation, pause him, and set his animation speed to 0% when he is just at the point of the animation with his sword outwards.
Then, every 0.04 seconds make hims face a direction and move to the position of the controller (explained later). Also make him deal damage base on (Damage of blade storm per second/25).
Ok, so basically you have him paused so you can't move him. So now you have to create a unit called something like "Cotroller" or something. Then, you create this unit when the hero uses the bladestorm thingy, make the player select it and viola, you have what you want!
If you still don't understand, basically, the controller is just to make you choose where to move your hero. Set its pathing, movement type etc to the same as the hero's so it is as good as controlling the hero. After the blade storm thing, remove the dummy, unpause the hero and something.