Hallis is not often seen in the common areas of Oakrest, preferring instead to remain in his quarters. He has never been a well dragon, as children of the Contagion rarely are, but a series of infections as a hatchling ravaged his immune system and turned it against him. Now that he is older, his tolerance to disease is quite high, but he has a severe autoimmune disorder that greatly affects his daily life. His symptoms are primarily neurological, and he is never able to feel warm, despite his tundra coat and a series of blankets he wraps around himself. On his very bad days, he bites his own tongue while he speaks and he cannot stop drooling, though most of the time his disorder manifests with shaking paws and a slight wobble to his steps.

Despite all this, Hallis is an extremely intelligent dragon whose understanding of geometry and space has led him to Oakrest to serve in the Citadel. He serves mostly as an engineer, knowing which sections of the tunnels are load-bearing and which ones are safe to dig through. All plans and architectural designs go through him before they are implemented.

In his spare time, he is fascinated by family histories, and he is Oakrest's leading expert on genealogies. Being the only known survivor of his own family, Hallis wryly admits that the general plague mentality of 'only the strong survive' is perhaps a bit overzealous. He would never consider his frail form worthy of survival, and it was due to how bad his disorder progressed that he left the Contagion in the first place. Instead, he chalks survival up to luck and canniness. He is deeply embarrassed when he meets other plague dragons, though he tries his best to make it a non-issue.

Other dragons are usually quite exhausting to him, as they often need him to repeat things - either because they are slurred or because they are above them. Hallis tries his best to be patient, but ultimately he retreats to his study where he and one of his several cats will curl up and trace lineages of note and read through building proposals both in Oakrest and abroad. He takes few visitors, though he always makes time for Eldritch and Copperlight whenever either of them stop in for a chat.