That movie was the shit. It had no right to be as good as it was until you realize that it was a movie made with love by true D&D nerds, designed to feel like the cinematic retelling of an actual campaign, crit rolls, weird player personalities, DM nudging, and all.
Xenk was great - that walking off bit was apparently because they hadn’t called “cut” yet and he just kept walking. So they let him, then turned it into a gag.
I think he was supposedly crafted as a replacement for a planned inclusion of Drizzt as a character, but I like my headcanon that he’s basically the DMPC sent to deus ex machina them out of their worst fuckups.