(taken from wiki- yes- I'm THAT LAZY.)
Abel is a light fair-skinned angel with a few of his father's features, such as his chubby physique and large, golden wings on his back. Unlike him, however, he has wavy and shoulder-length pale blonde hair, pupil-less amber-gold eyes, a gap in the top row of his teeth, and a halo with a slight wavy dent in it, which is typically tilted to the side to accommodate his hat.
His outfit resembles Adam's, only it appears to be mixed with pale yellow marching band attire. It includes yellow epaulets, golden buttons with pink straps and trim, and sleeves that fade from yellow to pale yellow. His visible arms are black in appearance.
His Exorcist helmet also looks near-identical to his father's, only with the horns shaping to resemble a ram's.
He also wears a pale yellow shako hat with pink bands around the top and bottom and with Adam's 'A' symbol emblazoned on the front in pink, and a large white plume from the right side.
Personality
Unlike his father, Abel is shown to be more easygoing, calm and benevolent. He also isn't afraid to speak his mind, as he shoots down Lute during the hearing regarding Sir Pentious' ascension to Heaven when she relentlessly cries foul on the matter-at-hand, and also mildly gloats about being the new head of the Exorcist army following his dad's demise instead of her.
Abel is also willing to make new friends, as seen when he along with Emily and St. Peter sings to Sir Pentious about Heaven's goodness in the song Like You during "Storyteller". However, the same episode also shows he's not very tactful and rather oblivious, such as when he unintentionally ridiculed Sir Pentious' name, and later tried to take one of Adam's guitars when Lute already was in a bad mental state.
It's implied that Abel never really received good comments or treatment from others, especially from his own father. For this reason, when Emily mentions Abel would handle things more fairly, Abel is seen blushing because of the compliment.