armor?

where is the forge master for obsidian armor? do i need prof to get it?

He's in the Fissure of Woe. Core area which is accessible from any/all chapters. Fissure (FoW) and Underworld (UW) are started from 3 towns and one shrine. Ch1: Temple of ages, Ch2: Zin Ku Corridor, and Ch3: Chantry of secrets.
The WIKI guide will fill in the rest