Looks very nice, what other games will be using the "Archon" engine? And what is it?
Well, while a lot of people license game engines like Unity et al because most of the work has been done for them, a lot of companies will build their own proprietary engine that will power a lot their games. Archon is the new engine Slitherine have made for their games going forward (not all of them, as some of their partner studios have their own engines as well).
Think of it when Creative Assembly upgraded their engine between Medieval Total War & Rome: Total War.
No other games that I'm aware of are confirmed to be using this new engine at the moment, but expect to see more going forward.