Marjan, Boogreism gives you 100 extra HP. I don't know if that affects future level increases, though.
"The gauntlet" refers to "running the gauntlet"...that is, running the Boogre's obstacle course. There's an intersting Idol at the end (Idol of Bongu) that gives some rather nice effects. Don't forget your Boogre brew! 1 per customer.
-Sazerac