Dungeon

And even if something overlaps, it's not a problem))). We can do it like this: let's say, Minotaurs: there will be 1 basic type and 2 upgrade lines for 2 factions, and simple Minotaurs can be upgraded along either of them, regardless of which faction's castle they were purchased in. This creates a lot of possibilities, such as a military alliance with recruits being sent from one castle to another. (by the way, such overlaps can be created for other factions as well, since we have many of them).