Quincy Solomon

Was a former king of hell, Mammon

Was bested in a duel during Etrigan's takeover and joined his side [Demon Knights era]

Once power was taken away, Mammon fled hell to avoid punishment, this however kinda sucks for humanity as the closer a person is to Mammon the more greedy they feel. 

As they have been away from hell for some time, they are far weaker which is saying much as they are still pretty powerful.

They have become an arcane hoarder who feeds off the greed of humans seeking power

Intersex, non-binary. Uses They/Them but masc titles like King and Sir

Horns and nails are gold, They also 'bleed' gold

Part of them losing their power has taken a toll on their eyesight.

Assume every part of their person has some kind of magic! you do not become the king of greed and an arcane hoarder without arming yourself to the teeth with magical items to fight back those who would try to steal or go back on a deal.

Two front fangs are also gold, Tip of their tail is also gold. Don't get stabbed with it. A person who is stabbed by their tail turns into a gold statue.

adding to the point above, Quin has some eerie life-like statue made out of gold. They are of humans or other demons who have crossed them and is set up as a warning to others who may try and trick them.

They go by 'Quin' or 'Quincy', Normal folk see Quin as a human, however, supernatural folk see them as a demon.

Like most demons, they view John Constantine as a pain in the ass and aren't too fond of the human as he doesn't have much to offer in trades. His soul is useless however he has bested them by playing to Quin's nature of greed. 

Mammon was an angel before they fell from grace, they have fond memories of having beautiful golden wings.

They have a rivalry with Giovanni/Raphael as he was the reason they were banished to hell. This bitterness carried on for eons until more was known about The Three Kings where they began working with one another.

They have a sense of what each person material desire is, this also extends to demons below their ranking. 

Although they embody the sin of greed making a deal or trade with Mammon isn't as bad as long as an individual lives up to their part of the deal or doesn't try to trick them. They see themselves as a supernatural businessman willing to give humanity it's greatest desires but at a cost. The bigger the desire the more expensive the price.