The city bank is run by miss Lisika (Lisa for short) and her employee's most of which were former debtors.
She acts like most of the city's well to do aristocrats, who also owe her a lot of favors, she also knows everyone's business having an genius level intellect...

Unbeknownst to everyone (Except other demons and devils in the city) she is a Raavasta Demon (A fox version of a Rakshasa demon) her close circle of staff are actually werewolves under her control.
She has been playing a long strategy game against the Dragon leader of the main city thieves guild for over a century, developing the other two thieves guilds to weaken it's resolve, simultaneously growing the city's wealth and moving hundreds of living chess pieces to gain power, riches, souls and powerful artefacts to ultimately gain control of the city to sate her natural demonic greed.

She gives off the demeanor of a motherly figure to encourage her game pieces feel like they can achieve something great or get themselves out of the debts they owe the city bank... But you don't realize the currency she's really dealing in is with your immortal soul, a Hero's soul is worth more than a beggars if you treat it like an stock investment!

Bonus points if you can work out what her sword cane has written on the blade in infernal...