Moximous N is a Yo-kai that looks like a dark shadow with yellowish-white eyes, the same haircut that Nathaniel has, and a cape-like appendage.
According to the first Yo-kai Watch Movie, he seems to have had a wild yet positive personality when he was alive (i.e, as Nathaniel). He is fearless and stands towards Wicked Yo-kai and he won't give up until justice is served. However, this changes to a quiet and curious type of personality as a Yo-kai. He always seemed to watch Nate when he was near him. In the game, however, you can see him as a hard-working person with the same personality of Nathaniel.
Moximous N has a skill called Victory Guts, which allows him to dodge many sorcery attacks. His special move is called "Mighty Moxie!", but however, his will not damage the foe but it will replenish all his health. Plus, he gets to possess himself, which gives him a high boost in all stats.
Moximous N is Nathaniel, Nate's grandfather who had passed away. He knows Nate and his grandmother very well as they are his family members. When he was around the same age as Nate, he was accompanied by a friend Yo-kai named Hovernyan. Not only that, but he has many Yo-kai friends that he had saved. This is because he always thinks of himself as a hero.
Moximus N is the mysterious guide that leads Nate to Meganyan in Harrisville in Yo-kai Watch the Movie and appears once again at the end doing the Moxie Pose.
When being recruited (Yo-kai Watch: Wibble Wobble):"You fought with courage and moxie! From now on, we're friends!"
"Moximous N" is a portmanteau of moxie (referring to the M-variant soultimate move), Moximous, and N (referring to Nathaniel Adams). This may also reference the fact that Nathaniel strived to become Moximous Mask therefore carrying his name.