The Development of Territories
Originally, territories were intended to be the equivalent of enchantments in Magic, but realistically, I've always thought enchantments had too much overlap with artifacts, especially when auras and equipment fill the same design niche. Since Domain has artifacts as well, that means the same overlap would be present.
Fixing that redundancy was a big deal to me. One of the things I wanted to do with Domain was to consolidate and streamline terms and mechanics that Magic uses to be more consistent; instants and permanents with flash were handled with the "quick" supertype, the "spell" card type consolidated instants, sorceries, and auras together, and "basic" became a supertype that could be applied to any card.
The breakthrough came when I got the idea to give territories strength and size like units, and allow them to be attacked. Now I could make a major game element out of protecting your territories! I felt like that didn't go far enough, though, and I was also struggling to change the feel of the game to a more Civilization-type of strategy game flavor.
At the time, Domain still used life totals as a win condition; don't fix what isn't broken, after all. However, it definitely was broken in terms of flavor, if not mechanics. That's when I started looking to other games to fix the problem. Pokemon and Duel Masters came through with inspiration for the current rules. From then on, I switched to a similar win condition, using face-down territories as the stand-in for shields or prize cards. At first, they were 0/1s, but I soon found that it made aggressive decks too powerful, and gave little reason to have more than 1 strength on a unit. 0/2s became the standard, then, and I think the game plays well that way.
Finally, there's the issue of making normal territory cards worth playing. Giving them spell-like effects when they deploy (like Abundant Wilds, above) was useful, but it doesn't really capture the flavor I want for the game. I expect the end result will be that most territories will serve as either some kind of engine for card advantage or combos, or as a win condition all on its own. Redridge Peak, on the side here, would be an example of the latter. This direction should make them valuable enough that protecting territories will be a major part of playing Domain.