Grond is a wrecked shipbuilder, who had found his way inside Ambrosia.
The Avatar was surprised to find a human in the Underwater City of the Gargoyles in Ultima IX. Grond explained how he'd come too close to one of the columns and a whirlpool had drawn his ship and him under sea, and he'd ended up there.
Grond tried for half a year to build a boat for escape, but with no wood available, that proved an impossible task, as rock was useless as a material for boats. Grond however was willing to trade some of the things that had survived the way down with him.