Mianite- The New Gods
In my opinion, there should be more than just 3 main gods. At least 5 main gods should be there, kind of like Primordial Gods from Greek mythology. Here are my top 3 candidates for the other primordial gods.

1- Kryonite: The manifestation of the cold, isolation, and silence. He was the one to give life to the cold breezes in the two realms that our heroes have landed in. He created the ice and snow, and all cold weather plants along with it. His domain is in the center of a glacier, on the exact top of Ruskomar.

2- Olymite: A female goddess, the one to bring the stars, and thaumic magic into the realm of Ruskomar. She is the goddess of the stars and planets, and the creator of thaumic magic. Those of Precantacia, Ordo, e.t.c.

3- Doranite: The god of secrets, and inventor of the specter keys. He gave the specter dimension to any who possessed one of the specter keys. He has a temple that shifts location under the earth.

That's just the beginning. The primordial gods are ones to rule Ruskomar, the ones to bring peace, and/or destruction. The minor gods are the ones who gave elements to Ruskomar, and the ones who, by instruction of the primordials, built the realm. There could be a whole family tree to write, but I'll leave that to everyone else to decide. Also, try and get the heroes to read this. It would be a shame if we only stuck with the same 3 gods until the end of the series.

Farewell- Kryonite