The monster-of-the-week eh, monster-of-the-year, EH monster-of-the-decade is introduced and explained, and yes, that is a real mythological being:
https://en.wikipedia.org/wiki/Brazilian_mythology

I looked up info, and contacted my Brazilian friend to be sure to get things right!

Honest confession: when starting out I wanted Boto to be female, but upon looking things up, Boto was always described as male, however several sources said that he's not picky when it comes to gender, sooooo.....