Thresh is bound by a will far greater than his own. The Ruined King, a sacrifice of a thousand thousand souls unto him, though he lay rotting on his throne, still enacts control over his people. Some to a greater degree than others. To Thresh he holds fast, for he is not inherently a loyal person. This compulsion to adhere to loyalty to the Ruined King is an artifice held together by a mandate that Thresh, for once, is actually doing something that will help in a way more so than running his jail.
Do not doubt that he loved doing what he did, for it brought him no greater pleasure in his life than to rule his little fief like a tyrannical lord. But he was a disillusioned man a long time before the great fall came. While others might remember the glory days of the Isles when it wasn't a terrible place consumed by its King in a mad bid for immortality, Thresh lived in a self formed shroud of darkness and terror.
He's always been jaded by the scorn his peers have leveled on him. Though in his line of work, someone has to get their hands dirty. He'd tasked himself with being as little of a burden on the kingdom as possible. More inmates meant more funding and personnel sent to the jail. So Thresh kept things minimized.
All of this did little to engender loyalty in the traditional sense. He was loyal to the idea, but not to the people orchestrating events of the time. Kings and people of power would come and go, Thresh would remain toiling away to further the cause in his own way.
People were not to be trusted, especially those drawn to the light. Those who stood before the light cast the deepest and darkest shadow. So he wasn't surprised when things went the way they did. Maybe at how things went down, but not that things had fallen far from grace.
This whole outlook and distrust of people has garnered him a strange dichotomy, loyal to the cause but not the people. Which in turn spawns his inability to forge true lasting bonds with others. Everything to Thresh is a potential tool to be turned against him or others around him. Loyalty to people is a falsehood that is easily exploited. An idea is resolute, can withstand the passage of time and the degradation of people.
Thresh is not above creating a link of loyalty between himself and others. He'll act the part out flawlessly than turn on his erstwhile ally in a fit of treachery and harvest their soul. For that is all Thresh sees in people. Souls.
So, in short. Yes Thresh is loyal. To an idea. Woe betide the person who thinks they have the specter chained by loyalty. He's a wily one.
