The stupidest decision in the series?
Got to MoI on my first re-read of the series. It's been a while since I first read the books, but I feel like Toc The Younger running off to join the Tenescowri at Bastion has gotta be one of, if not, the stupidest decision anyone makes in this series.
He leaves his superpowered companions to go hang out with the evil-ass rape and cannibalism army, knowing damn well they don't have normal food, starves for 3 weeks, draws the attention of the Seer, and gets himself super-torturted for it. Obviously, he couldn't have seen the torture part coming, but what did he expect was gonna happen hanging out with the Tenescowri?
I'm sure there are worse decisions in the sense that the chain of events it causes are more catastrophic, but with the information Toc has, his choice seems comically stupid. He could have been hanging out with Tool and flirting with Lady Envy all day. Maybe she'd even let him hit one day (I doubt it...). Instead, he ends up cuddling with the K'Chain Che'Malle Matron.
Let me know in the comments if there are any decisions you think are more fitting for the title of stupidest. I remember there being some in TtH in Harllo's plotline that really got me going at the time, but it's a bit blurry.