Spear of midnight black
From Wookieepedia, the Star Wars wiki.
The spear of midnight black was an ancient dark side Force power. It enabled the Force-user to summon the Force and forge with it an invisible spear from dark side energies which could be hurled at opponents, killing or injuring them as if it was a real physical spear.
It is possible that Kyle Katarn used this technique to kill Dark Jedi Boc Aseca in their duel in Valley of the Jedi on Ruusan, forging a spear of midnight black and hurling it at a momentarily distracted Boc's chest, much to the delight of the Sith spirits that were trapped in the Valley.
[edit] Behind the scenes
While this technique is not available in the computer game Dark Forces II: Jedi Knight, it is described in the novel Dark Forces: Jedi Knight as the method that Katarn uses to kill Boc. Of course in the game, Boc is killed simply by the lightsaber duel.
