I broke out my SC manual and heres what was written:
Protoss History:
"Although only fragmented documentation remains, ancient Protoss texts speak of a highly advanced race that ruled over thousands of worlds in the galaxy, tens of millions of years ago. Nothing is known of the origin of the Xel'Naga, save that they were not native to the galaxy over which they held sway."
Zerg History:
"The pride in their achievements proved to be the fatal downfall of the Xel'Naga. The Overmind, while slowly expanding itself into the void of space, became aware of the mighty Xel'Naga world-ships hovering ominously above the skies of Zerus.
The Xel'Naga, having kept a constant watch on the Overmind, were horrified to find that it had actually severed their psychic link, effectively hiding itself from their view. With its need to consume driving its minions into a lustful frenzy, the Overmind launched the now space-faring Zerg swarms at the unsuspecting Xel'Naga.
The ancient race did what they could to stem the tide of the ever-advancing Zerg onslaught, but in the end their efforts were in vain. Wave after wave of Zerg swarms hammered the reinforced hulls of the Xel'Naga's ships with no signs of abatement. Within only a few hours the Zerg overran the defenses of their creators and laid waste to the Xel'Naga fleet."
It appears that the manual said that the downfall of the Xel'Naga was from the Zerg. It suggested that the entire race was wiped out.
It doesnt really say if the fleet was the whole society of the Xel'Naga or just a fraction of it. I think the entire race, except for maybe a few, was wiped out. Why didnt the Xel'Naga, if some of the race did survive, do anything about it after the Overmind layed waste to their fleet?
