Darius

"As current king of the city, Darius is “the man.” For your purposes, though, he’s the guy with the Power Social objects. Meet him in a district’s VIP room when he arrives at midnight and he lays one of these powerful tools on your Urb." - excerpt from The Urbz: Sims in the City Official Prima Guide

Darius is an Urb residing in Miniopolis in The Urbz Handheld and Urbzville in The Urbz Console.

Handheld
In the handheld version of The Urbz, Darius is the leader of the Rep group called the Streeties. He has the highest rep out of anyone in the game his face is seen on billboards, which reveals that he is famous on a citywide scale.

Console
The player Urb first meets Darius through their friend will.i.am at their new apartment, where he asks them to show him a Power Move. He is seen throughout the city on billboards and posters in Urbzville as well, though they will change to the player once they reach a certain Reputation. In each district, he will arrive at the VIP Room at approximately midnight, and if the player urb has a high enough reputation to get past the bouncer, Darius will reward them with a power move that can be used to get rid of that district's villain.

Once the player urb has defeated all the villains in each district and collected all of the pieces of Darius's Secret Machine, a cinematic will play where Darius gives the player the key to his penthouse, unlocking it to live in. He then retires to his blimp to travel to Miniopolis (the setting of The Urbz Handheld), but will still send the player messages and arrive at the VIP parties.

Trivia

 * In the console version, Darius will stay at the VIP parties until 3-4 am.
 * If the door to the VIP area is blocked, he will teleport into the room with a special animation.
 * According to the Prima Guide, Darius is the one that sends reminder messages to your XAM to warn you that the rent is due soon.