Ymir and his son Jotun are Paradise Falls's pair of knuckleheads. Jotun has difficulty forming basic sentences, while his father is a jovial madman, armed with a horrific-looking super sledge, like his son's.
He seems to be very awkward and unsocial, responding vaguely and briefly to the Lone Wanderer and only responds to fellow slavers with grunts. His father has always been very proud of him and constantly praises him, bragging to the other slavers about him, which Jotun seems to find quite embarrassing.
If his father, Ymir, is killed then Jotun will become frenzied, attacking anyone on sight, including his fellow slavers. As he is heavily outnumbered and usually only carries a super sledge, he typically dies almost immediately.
Jotun seems to be one of the few slavers in Paradise Falls that goes to sleep in the slavers' barracks during his daily schedule, the others being Crimson and Clover in Eulogy's Pad.