So, lore speculation, what are we, the player? The "core health" mechanic is rather esoteric, and the fact that we can't fight is also strange. plus, the fact all of our followers revive on death after each excision, even though the only other way to do that is with a Incarnator and even that can't fully restore someones health. and also I should mention that our followers are extremely loyal and don't seem to mind being killed or replaced. none of it made sense of me, until I remebered that the Adjudicator of the Hunt called us a "traitor". So, basically, my theory is that we are a boss monster that enthralls other followers, like the Fireworks Master or the False Sun, and we have abadoned the dragon to maraude across these wastes. Maybe we're like a "Core of False Hope".
on a unrelated note, It would be cool if there was a small random chance that instead of the normal encounter you'd fight your team from a previous run at that depth, with a "core" at the back that has zero attack and health equal to your core health from the last run.