"Immortality isn't as good as it's made out to be."
C A N O N
Monday was created as the youngest of seven 'superior' Denizens; the ones who would later become the Trustees, they were all created by the Architect save for the eldest, Sunday; he was the product of a mortal woman and the Old One.
Eventually the Architect left, leaving behind Her Will; the Trustees chose not to follow this and split the Will up between them, each wielding a Key and presiding over a demesne. As a consequence of not following Her orders, each Trustee was inflicted with a Deadly Sin that plagued their every move.
Monday was inflicted with the Sin of Sloth, and as a result his demesne, the Lower House, fell into disorder-that is, until his part of the Will escaped and sought out the Rightful Heir.
Arthur Penhaligon, an eleven-year-old mortal from the world called Earth, set out (reluctantly) to set things right as ordered by the Will; after defeating Monday, in an act of charity the Heir cured Monday of his Sin rather than destroying him as the Will urged, returning him to his former self.
And a few nights after that, he Woke up.
N A U T I L U S
Monday has been through quite a lot. He suffered through trying to avoid being burned alive by his clone during the reality shift in Nautilus, and formed a friendship with Nash along the way and went back to discover that the House was in turmoil and narrowly escaped his own death, thanks to Ratchet's aid.
And after lots of other things which I will add later, Monday's current status is trying to deal with his cranky teenage son former second in command, Noon, prepare for the upcoming battle with Isis, and trying to keep his restlessness under check.
HE'S A DERP. A HUEG DERP actually wait no
Monday is quiet, mostly calm and kindhearted for a denizen; he feels that because of his past actions, he isn't a good person. He's sort of an awkward turtle in the whole 'social relationships' department, but he's getting the hang of it.
He loves tinkering and experiments, some of which tend to backfire on him spectacularly. He's like a Victorian mad scientist or something.
He also loves mortal technology. Loves it to bits, he's kind of astounded how mortals can be so creative and he just gets so excited about stuff like modern cars and motorbikes. (b-because in his time HORSE AND CART L-LOL. 8| )
He can fly as of the Heartless Event.
He is a decent swordsman.
He's had military training and experience.
He's fairly quick on his feet, with above-average reflexes.
He's experienced with Bending, as he uses a variant of it in his own world.
UPDATED LATER ORZ.