The Dodechahedron is a resident of Digitopolis, and knows a lot of maths, however is not very logical. He leads the way to Digitopolis, through the Numbers Mine. He also tells Milo the importance of perspective and importance of math.
He doesn't like goodbyes as he used his sad faces when it was time to say "goodbye" He also knows how to calculate but is not very good at reasoning. He is friendly but believes names are inefficient and individuals and objects should just be called by their type/species.
The Dodechahedron has twelve faces and uses one at a time. He has
a smiling face
a frowning face
a laughing face
a crying face
a pouting face
a thinking face
a sighing face
a wanting face (maybe) a sleeping face