So just to summarize what's on the cards that are already in the set:
0) The Starstill, an ancient event in which the plane stopped moving about its sun, has divided the plane into two terrible extremes, a scorched desert (Illpyre) and a pitch-black tundra (Frostwynd). The border between the two, which is probably relatively habitable, is named or has a place named Maraka.
1) Illpyre has one or more white groups that probably worship the sun. Elori is implied to be the name of a deity or something. Some of the devotees are humans, some of them are humans that are also enchantments, and some of them are enchantments that aren't humans anymore. This is definitely the faction with the most flavor text so far.
2) Starstill, which is also the name of the plane, has mechanical entities. They don't understand enchantments.
3) Frostblight is probably the name of a place in Frostwynd. It has some connection with artifacts, and there are relics there, which at least one blue human enjoys scavenging.
4) Glacinorak is an ice dragon who, along with his or her fire-flavored brother, caused the Starstill because he or she wanted a more suitable climate for himself or herself. He or she has a card, but his or her brother doesn't yet.
5) There's a serpent in the set. I don't know where it lives.
6) There is a black human rogue living in Illpyre. That is literally the extent of black's worldbuilding.
7) Frostwynd has a red human barbarian that likes the cold and has poor judgment regarding weapons.
8) Illpyre has red viashino and elementals. The viashino we've seen is a scout, which probably implies some form of organization? But there are no goblins, and let's keep it that way!
9) All (?) the trees in Frostwynd have been standing since the Starstill, and there is a green group that can talk to them.
10) Spirits exist, so far in green and white.
11) There are druids, or at least there used to be and they left behind a relic.
So there's plenty of room to work with.