Maresh is referring to events that took place in Chapter 7.
Today in exciting comics that you should read if you like The Water Phoenix King is Absolve All Hope, a short (32-page) supernatural action comic with some fantastic fight scenes and an incredible grasp of how to lay out a page. You can finish it over a lunch break, so go check it out.
If I assume rusty Latin base “exis vaco” sounds strikingly similar to, “empty head” or “out of head.”
Somehow fitting for worshippers of a dead god who glorified willful ignorance and fear of knowledge.
I’m just gonna throw out a suspicion that the green clad guy with Maresh & Dosh is a disguised Varaxunax who has finely been coerced into joining up with Maresh.