: The why did the Dark destroy the knot in Covenant
What's that, a rhetorical question? It has nothing to do with the paragraph you quoted.
I don't recall the dark destroying the knot at covenant in the game, so perhaps it was hidden in a flavor text? As for the dark situation:
"But we can't wait for them: There is a World Knot west of the Cloudspine and The Head insists that the enemy has learned to travel through the Knots. If we don't destroy this portal we might hold the mountains only to be outflanked by forces emerging from the Knot behind us."
If the knots DID connect to multiple locations, then the light forces could have left Covenant by the world knot and taken that across the cloudspine. But it doesn't and they didn't.
--Stinger