Stoic, logical, probably grumpy.
Arbiter could be described as having a relatively flat affect, her expressions are fairly subdued, and those that she shows most obviously usually tend to be negative. Her sense of humor can be somewhat twisted, and she's definitely a fan of sarcasm. At times she may see others' feelings and reactions as somewhat of a game that she can play -- the likelihood of this happening gets larger the more ridiculous she sees the person.
Arbiter is very big on promises and loyalty -- if she gives her word, she keeps it, but if someone breaks theirs she'd be happy to burn them down. No second chances. Gaining her respect is something that's earned, though she'll begrudgingly give (some) of it to those in positions of authority over her if they haven't earned it yet, but it's tenuous at best until then. She will do her duty as expected, going beyond it if rewarded but only the bare minimum if not.
Want to be her friend? She's a fan of those with power, whether it be by rank, size, or prowess. Unsurprisingly, she's not much of a romantic either. She keeps most wolves at arm's length, deciding whether or not she can use them, so it seems likely that if she ever chooses a mate it will be a wolf that appeals to her ulterior motives at the time. Oh yeah, that whole loyalty thing? Yeah, uh, not a fan of cheaters. She'll cheat in a fight though, that's totally fine.
GIFable as
Aeryn Sun from Farscape