Interloper chose Pallas as his secretary for two reasons. The first is his social skills are horrid and he's so bad at talking to people younger than him, so he was able to vibe with Pallas pretty quick. They bonded a lot over drinking and sharing stories of their lives or heroic tales they heard. The second is that she serves as his personal trainer when it comes to physical fitness so he can become less of a lame old man. Mostly however he just REALLY needs someone to talk to or else all the paperwork will make him pass out from boredom.