ToME: the Tales of Maj'Eyal

So I made a sawblade, played him for a dozen levels. Tried to google the answer to this question. Got some random post by someone assuming it was unlocked just by having the dlc. So I start a new doombringer in the AoA campaign. I have the choose your escort add-on installed. Get to my first escort, see the default 8 choices. Apparently tinker escort has an unlock requirement? Do I have to beat EoR? Or just a certain quest threshold in EoR? it's not listed as an unlockable at all on the wiki.

According to a previous thread like this, you unlock tinker escorts by beating Sunwall Outpost with two different tinker classes.