Quote Originally Posted by philby View Post
when was it revealed or explained? or is it at 'fan theory' stage?
I don't think it was ever outright explained.

In Spotlight Metroplex, he was protecting "it". I think most people assumed at the time that he was talking about the Magnificence.

In the Ironhide TPB, I think Alpha Trion said that he and Metroplex were filtering the atmosphere on Cybertron, which is what made it habitable again.

In Dark Cybertron trades, I think Windblade, Chromia, and Nautica explain that they took over the care of Metroplex from Alpha Trion. At that time Metroplex was carrying one of the ores.

So, I think it's generally just people taking 2, 2, and 2 and making 5. Until such time as John "Continuity" Barber decides to make something more of it.