Size class Giant
Boss perks Vitality prowess, charisma prowess, arena manipulation, phylactery, hybrid, empowerment, shapeshifting, enchanted armor, enchanted weapon, perception prowess
Minion races Humanoid, celestial
Minion size classes Human, Colossal (only celestials)
Mooks Soldiers (100), clerics (25), slaves (50), recruiters (25)
Elites Warriors (10), craftsmen (10), agents (20), battle mages (20)
Lieutenants Chosen, Hunter
Minion perks Sustenance, training, faction
Realm perks Expansion, hidden
So perhaps this other realm of unknowable madness stuff shares the same technology/acoustics affinity, and the character has been infected or otherwise changed as part of the vanguard invasion. Robot Cthulhu. I can dig it.
The realm can't be found except by people who know exactly where it is, and it's slowly expanding across the world. That says "some black hole sort of pocket dimension" to me. One day you walk in to town and... it's not there. You keep looping back to where you started, or to other places nearby, as if the world was a scroll that had been rolled back in on itself.
This is probably deliberate. Maybe the Eldritch Machines can't manifest well except in "prepared space," so they're drawing the whole world in.
Our character is big, but not excessively so. Somewhere between ten and twelve feet. And it does not look human. It's a machine through and through, and "looking normal" has taken a backseat to pure functionality. It can repair itself quickly in the middle of combat (nanites or something? or maybe this is a reflection of its alien nature, and it just happens to be a machine that heals like a biological organism).
As if there's a software back-up, there's some object that has to be destroyed in order to kill it for good. Maybe it's like a remote power source, and it'll keep regenerating way too quickly to be destroyed so long as it has that power. Also, it can control the physical make-up of the entire realm for as long as it's alive/functioning. The character, the realm, and its (sufficiently converted) inhabitants are in some ways a single entity, and the realm sustains their lives until it fails.
The Invaders are going to have a problem with bringing this thing to heel, but it's going to be a tough thing to beat if/when it succumbs to madness itself.
(I wonder if all of the Eldritch Machines were created this way, or if hybrid things like the character are rare)
There are slaves in this realm. I'm ruling that there's a slow conversion process that happens over time to people that live here, and the slaves are the ones whose minds don't survive the process. They're P-zombies, devoid of self-awareness. Those that make it, though, are under the "celestial" category. The Invaders aren't just from a Weird Place, they're from some kind of afterlife. Heaven is the Machine World or something. And the converted celestials have multiple faces. Sometimes they've got just a couple, maybe even arranged around their heads like Janus, and sometimes it's like somebody put a bunch of faces together in a roughly human shape.
Medical and magical knowledge is held here. There is some kind of religious element here, too, probably with (some of) the inhabitants worshiping the character. Most of the magic is in enchantment. The most skilled are trained to leave the realm for surgical strikes and espionage missions. And two individuals in particular have gained notoriety: a paladin, "chosen" of the character and probably somewhere in the middle on the (technological) conversion scale. And a hunter. Between them it looks like there's an emphasis on rooting out Bad Things, both at home and abroad.
One thing that's inevitably lost by this realm's inhabitants is the freedom to choose. They may have agency elsewhere but they become incapable of betraying the character soon into the conversion process. Literally incapable. Even if they want to, it's simply a thought process that they cannot complete, like trying to imagine infinity.