A.N: I guess this is becoming a bit of a trilogy now. I'm not entirely sure who the voice is in this, but my best guess is Tal from the Dark Forces novellas. Go read them, by the way. It's well written and it's got amazing art, including Jerec rising from the center of the Valley on a column of pure black.
Boc had fallen and now there was but one dark Jedi left. The unsettling thrum in the Force that Kyle had felt as soon as he'd entered that catacombs suddenly escalated and the dome at the center of the chamber began to explode outwards. Amongst the stones, surrounded by a pillar of blackness despite the light flooding from below, rose Jerec. His body was wreathed in dark power and even the rise and fall of his chest made the Force ripple with the cry of tortured souls.
Jerec had harnessed the power of the Valley of the Jedi, and Kyle could no longer stop him.
Hold, young Knight, said a voice sounding from the depths of time. Though tinged with the pain of Jerec's taint, the voice was strong and Kyle felt as if the owner was standing just over his shoulder.
All is not lost. You are a Jedi Knight and as such, hope comes with the territory. He is powerful, but it is new to him. He does not have control and this makes him vulnerable.
Kyle felt incredulous at this, Jerec's sense in the Force seemed to be an impenetrable black wall; large and terribly oppressive and pressed at Kyle's mind from all sides.
He is not invulnerable. If anything, he is far weaker than before, for he has to contend with the will of every soul in the Valley, including Lord Hoth, Kaan, and myself. He is feeling unbalanced and will put on a show of confidence.
"Ah, Jedi." Jerec said with is shark-like grin. "I hadn't expected you to make it this far, but now you are going to witness the beginning of my dominion." Every word was echoed with the shadow of many sobbing voices. Jerec descended to the ground in front of Kyle.
You see? Vainglorious boasting instead of simply getting to the matter at hand.
"You see," said Jerec as he drew his lightsaber and gestured towards Kyle. "You are weak." The gesture, even without any power behind it, caused the Force to cry out with a thousand voices of pain.
Now taunt him. Something short and witty, for preference.
"Says the man who needs the power boost to fight me." Kyle replied on the spirit's advice.
Jerec's laugh took on a sinister edge within the Force as it curled off him in dark tendrils, shaking in time with each chuckle. The sensation was unpleasant.
"You are weak and alone. What foolishness makes you think you can stand against me?"
Say as I say. I am not alone.
"I am not alone," said Kyle.
My ally is the Force.
"My ally is the Force."
And it is a powerful ally indeed.
"And it is a powerful ally indeed."
Jerec roared in anger, echoed in the Force by the screams of trapped souls, and lunged. Kyle brought up his saber to meet him.
Now the rest is up to you, young Jedi. May the Force be with you.
And a battle was fought.