Artie is a big iron golem. They first appear in episode 22. Into Avelis (Part 13) at Torva's Jaw, when they tell Falen that his father is looking for him. Falen tosses a book (which turns out to be Goddess' diary) for Artie to bring to the vault, and that's where we follow them to. Artie is an artificer for Torva.
The Guardians follow Artie and see them in a messy, yet orginised room with three desks, chilling in a chair with a cuppa tea. The room reeks of dark energy. Since Artie is but a mere golum, and cannot really drink tea, but only spill it, the chair beneath them is all stained with tea.
Artie does not feel, neither do they have a sense of taste. Artie is not easy to fool (not that the Guardians have really tried), and cannot be affected by magic or non-magic. When Corbin addresses them as "my sweet metal boy ", they point out that they do not have a gender. Artie is very objective and is difficult to pursuade, but does not attack. They inform them that the vault is downstairs, helping the Guardians on their quest in finding artifacts.
Basically Uncle Iroh from Avatar: The Last Airbender.