A big, loveable goofball, he does his best to off-set Charon's gruff, smarmy demeanor by being as warm and welcoming as he can be. He himself was adopted into the pack, after his own sent him on his own way- not born of them, and so tries to make everyone else feel welcomed and accepted into his newfound family. Charon was...not the best at doing so, and Atticus was one of the first to join the pack from the outside.
Smarter then he lets on- but often so in his own head it's hard to prove that. He's a silly, fun-loving pup at heart, and refuses to grow up.