The one that fell from the heavens, Lucifer is bitter and resentful not only towards his own God, but to every other egotistical, power-raging deity. To humans, he despises them, and takes joy to give them a bastard smile and mess with them - there's a reason why humans sometimes blame him (or, Satan, whom he's not, but doesn't correct that often) for everything wrong in their lives.
Lucifer does not meddle in the affairs of humans or gods. He is the "other" party. He bows down to absolutely and positively no one. He takes everything with a grain of salt - after his exile, he's stopped caring. Underneath the introverted face and the impish, sarcastic remarks; his rage and the feeling of betrayal still boils as if he was cast from heaven just yesterday.
When forced to interact with mortals or others, he is known as Luce.