Gargoyles: The Dark Ages, often abbreviated to The Dark Ages or simply Dark Ages, was one of six proposed spin-offs, a prequel to Gargoyles taking place in Wyvern, Scotland in the years between 971 and 994. It was pitched to CBS, but not picked up.
Dark Ages would have been set at Castle Wyvern, beginning when it was built in 971, upon Kenneth II becoming King of Scotland. It would deal with the beginnings of the alliance between the Wyvern Clan (then under Hudson's leadership) and Prince Malcolm, with Hudson and Prince Malcolm in the lead roles, Goliath, Demona (at that point named "Angel", short for "Angel of the Night"), and the Coldtrio in supporting roles, and the Archmage (who is allied with Iago) as a villain (although presumably one whose true nature has not yet been revealed to the Prince). Hudson's mate would also be significant (considering her death also occurs in 971). The trio are only children at this point, and would most likely have had a minor, possibly comic-relief, role. The Illuminati would also have had a role, likely as antagonists.
The series would have, if it had been made and continued long enough, covered the story of the Wyvern Clan between the foundation of Castle Wyvern in 971 to its fall in 994, including an account of how Princess Elena and Prince Malcolm died. (Greg Weisman has mentioned having strong ideas for how those events took place, but has not revealed them as yet.)
Greg Weisman wrote a piece of prose fiction entitled Once Upon A Time There Were Three Brothers..., which serves as a sort of lead-in to the series and can be read here.
At the 2008 Gathering of the Gargoyles, Greg revealed that he has a Dark Ages story in mind for the next six part Gargoyles mini-series. This story would be told after the conclusion of the Bad Guys: Redemption story-arc, assuming the mini-series comics continue at that point.
With the gargoyles in 10th century Scotland largely nameless, Greg Weisman planned to use names to designate characters for the writers, artists, animators, etc (such as he did with Othello, Desdemona, and Iago on Gargoyles and Second, Sacrifice, and True (along with many others) in the SLG comic). If that wasn't feasible, Greg planned on having Prince Malcolm name every gargoyle with a biblical or mythological name, so that the humans on the show (and the audience watching it) could use those names while the gargoyles continued to ignore them.