Heroes 6 - Discussion

First, why can't the sky be the third tier?

A hero rides a horse across the sky, followed by his loyal peasants and flying archers. He plants a flag on a celestial sawmill, processing celestial wood, and collects a pile of sulfur from the nearest cloud.

And secondly, I would prefer it if the third tier was underwater, and consequently, a race of underwater creatures.

A Naga rider on a Naga plants a flag on a seaweed harvester, defeats a legion of guppies, hires jellyfish, and upgrades them to jellyfish captains in the nearest water fort.