This is the only thing available to play "Empire" using Age of Sigmar Rules, if you want to play using the ruleset, and set in the World That Was
https://www.games-workshop.com/en-GB/WSC-EMP-ENG
Aren't those the "old" warscrolls from when W:AoS started?
Not quite, it's an updated version which doesn't have the warscrolls for most of the units that are now in other factions, and has generic warscrolls for formerly named characters. I think they did it to move on from the old fluff, as they no longer do those miniatures, and want to support the current lore.
I had intended to find the link for the Empire warscroll compendium from launch, which I have my own copy of, but it doesn't appear to be on the GW site any more.
Since then they have a Warhammer Legends section on the Warhammer Community site. Where I believe they will do a new-old warscroll for the old that was Armies, including renamed units, so that they can be played as an old style army. They said when each one launches there will be a Made to Order for a selection of OOP minis for each faction. At the moment they have only done one for Dark elves
https://www.warhammer-community.com/legends/When Empire comes up, I'll be sure to let W-E forumers know
That's just the warscrolls, for points, they'd only be in the now OOP General's Handbook 2016.
So does that mean, since it is OOP, that it is now useless after only 2 years?
Yes and no. GHB2016 was the only one so far with the points for the old Compendium Warscrolls. They didn't put in points for those in GHB2017. The General's Handbooks are primarily going to be an annual for the matched play points updates -presumably for factions still in the game, so a re-balancing of the game if you like, something much requested, along with freequent and quick FAQs, (something they are getting better at)
It's more than just a points update, it includes new scenarios and optional rules for open play, narrative play as well as matched play
In the Age of Sigmar Setting, the former Empire miniatures that are usable, are now split into a number of factions - Devoted of Sigmar, Free Peoples, Collegiate Arcane and Ironweld Arsenal. You'd need the Grand Alliance: Order book, and the latest General's Handbook for points. (And there is a new one out at the end of the month)
So there are now 4 Empire like factions? 
Well maybe 5, if one includes the Stormcrud Marines?
Empire isn't a faction in any sense any more, not unless you're playing a game set in the Old World
Armies are built with a common Allegiance. For example, Free Peoples is an Allegiance, in that faction are the freeguild troops - Freeguild Guard, Freeguild Handgunners, Freeguild Greatswords, Freeguild Generals etc. If you take Free Peoples as the allegiance, you get access to specific Allegiance abilities, command traits and artefacts that represent how that faction fights. At least 80% of your army has to have the FREE PEOPLES keywords, to count as that allegiance, and you cn have up to 20% allies, and the allies chart means they can ally in Collegiate Arcane (Battle Wizards and the wizard wagons), Devoted of Sigmar (warrior priests, flagellants, witch hunters, war altars), Ironweld Arsenal (war machines, helblasters, helstorms, plus duadrin war machines, cannons, organ guns, gyrocopters, and the Steam Tank). Also, As Free Peoples are an ORDER faction, they can ally in Stormcast Eternals.
Alternatively, you could build your army with an ORDER grand alliance Allegiance, and mix and match any ORDER keyword troops, though the allegiance ability and command traits and artefacts will be more generic
So you could sort of build "Empire" like armies
So does that mean I'll be waiting three weeks for the answers to the questions above? 
No, most of those answers are unlikely to change before then, and I was meaning before we write up an FAQ thread
