What I've got for the Collectives new history so far

During the Universal War, the Collective inadvertantly collided the Primary Universe with the Secondary Universe as a result of the usage of a new piece of technology in an attempt to end the Universal War. This result in many storms erupting across the universe which have completely destroyed an unknown number of sentient species. In addition, this rendered the traditional means of Collective inter-galactic travel completely impossible, and standard travel across the galaxies implausible due to the dangers arising from 'tears', holes in space time where the Primary and Secondary universes have collided. Another effect, coupled with the effects of the Universal War, was the near complete destruction of most extra-galactic holdings across the universe. The storms disolved quickly in the milky way, but not before devastating entire planets and wiping out many different lifeforms across the galaxy. The effects of this collision are estimated to last a further 500,000 years These tears weakened not just the barrier between the primary and secondary universes, but other universes as well, and this allowed for the arrival of more extra universal entities
In short, the Collective caused a universal apocalypse in their attempts to end another universal apocalypse.
As a result of this, the Collective could not reach it's extra-Galactic holdings, and as such they fell one by one as their defences failed and no reinforcements came from other galaxies. They were picked off one by one. The Collective was locked in a losing battle for many, many years. Tens of millennia passed before the tide finally turned. Armed with a refinement of the piece of technology that caused the Universal Cataclysm Disaster, finally perfected after many Triarian Lifetimes of work (Thousands of years) they were able to destroy the extra-universal threat and finally 'reclaim' their own universe. And what was left of the Collective, drastically reduced in size, man power etcetera, stood upon an island of corpses in a sea of blood. Although brutally beaten, they had held.
For the first time in living memory the section 'The Greater Good Prevails' was played. But there was no celebration. Everywhere one looked they would see death, they would see decay. Everyone had lost multiple family members and many had known only war. As such it was branded the single most horrific war in Collective History. After the war, a recording of the traditional Umbrae Populus song, Dium'zul, became the number one played audio track within the Collective and remained so for many cycles.
"Dweade a doi e'tol
Mi dium ond zia.

Diwethaf'wym soli'un nod ywr
url'kise gaefa troi at card iar

Dweade a doi e'tol
No'l Card'aid bachk er soli'on rro nod ywr
Mi dium ond zai 
Hurl'wym er pam gollais aid"