Giants weren't completely unheard of in this world. In the Western Frontier there was a village of Forty-Foot-Tall Cyclopes spawned by the Nobility
Dynus is a giant. And Mountain Man Seurat is one as well.
There was a race of giants who were also spawned by the Nobility that came into conflict with them. It was said this race was one of the things outside of the Nobility that gave them a struggle to battle. The scene of the battle is the Lightning Thicket of the Gods described in Iriya the Berserker.