I’ve always had this battle as the epic battle to end all battles. I’m sure each group takes its own interpretations of it, of course.
I follow the novels in regards to the elves, who switched sides on the eve of battle once they saw whom they were fighting alongside and realized the true nature of Azrai.
I also view the ‘tribes’ not as one large band per culture, but the entirety of that culture up and fleeing into Cerillia.
One time, I had the party accidently thrust through time and had them show up at various points in history both past and future. It made for interesting play and conjecture. But eventually, I had them ‘accidently’ thrust into Deismarr. Although they got there with the battle already underway.
I had the fight ranging at the foot of the mountains and ranging up and down the sides of quite a few, spilling over into the valleys in between. Prior to all this, over the course of months, the elven, goblin, gnoll, orog, and Vos armies began to converge and drive the Alliance back into the land bridge, working seperately at first. They finally converged and shoved the Alliance into the foot of the mountains, which is where the Alliance poured everything it had into one final stand. Unbeknownst to all, the beastmen & Adurian army began to come in from the opposite side of the mountains.
Overnight, the elves switched sides and stood alongside the forces of good in the morning. The Cerillian contingent of Azrai slammed into their front, while the Adurian forces of Azrai spilled over the mountains to hammer at their rear.
Despite the elven assistance, I had the alliance steadily losing. Hence the need for the deities themselves to step into the fray. It was at this point that I had the party show up, with the lines blurred and ranging for miles. I had a few Cerillian dragons on either side as well.
Above, I had the gods battling in giant form across the heavens while their champions clashed amoung the mortal forces below. It was cool to watch the players glimpse their future deities as all too mortal humans, struggling as much as they were. At one point, I had a gigantic shield dozens and dozens of feet wide slam into the earth, shattering allied and enemy lines. The players looked skyward, and could no longer see the gods fighting clearly. They did see vibrantly glowing clouds of light (one per deity) swarming around a much larger, darker stormcloud (hmmm), from which they could catch glimpses of the deities struggling.
One glowing cloud began to sink and fragment, as if mortally struck. At that point, all the clouds merged into the dark one after a slight pause. Combat swept the pc’s away again, as they tried to influence things that mattered to them. One PC rushed to fight alongside the elves, another strove to reach the side of Roele, etc. Anyway, then the gods all perished as one. The divine explosion hammered down the slopes, sweeping aside allies and enemies with impunity. I had secondary explosions center around each champion, with descriptions fitting each patron god (lightning for azrai, fire for basaia, etc). The survivors were scattered, the majority of the forces destroyed, and the land bridge itself began to fragment and sink (although this took a full day). I used the divine explosion to thrust them foward through time again, leaving a rather stunned party who seemed pleased to have apparently contributed in some small way to their favorite historical whatevers. Of course they were at this point in the future, which led to its own problems. But I won’t go into that unless asked.
All in all, I like my interpretation. Flame away, if you like. I stand by it 