In Venore, two floors below the central depot, eastern side.
He hangs around the tavern and offers a game of dice.
You can bet from 1 to 99 gold and if the dice lands on 6 you get 5 times your bet. You may also bet 100 gp for a chance to win a die. Similar to the main money gambling game, if the dice lands on 6 you win the dice.
If you want to play with him, you must say: "dice" - "money" - "(any number from 1 to 100)".
There were rumors that you can increase your chance to win a bet with him if you wear a Wolf Tooth Chain, but it was proven false.
The chance to win is 1/6, so you will lose money in the long run because you will only win 5 times your original bet on a successful roll (unless you play for dice and can sell it for more than 600 gp).
He has a cousin named Hugo.
Player: hi Zebron: Greetings, high roller. So you care for a game, Player? Player: job
Zebron: Oh, I am just sitting around here and gamble now and then. Player: name
Zebron: I am known as Zebron. Player: time
Zebron: It is exactly 11:38 am. Player: king
Zebron: Ah, our beloved king! Bless him for the gambling licence of Venore. Player: Tibia
Zebron: What would I need more than that what I can get right here? Player: army
Zebron: Hehe, they spent a good part of their salary here in the tavern. Player: tavern
Zebron: It's a fine place to be around, isn't it? Player: game or gamble or dice
Zebron: So you care for a civilized game of dice? Player: swamp or amazons
Zebron: Bah, always the same chitchat. Swampelves this and amazons that ... blah blah. Player: Excalibug
Zebron: I would not bet that anyone will ever find it. Player: Carlin
Zebron: Carlin, the beerless ... what a shame. Player: Thais
Zebron: Thais is a bit too conservative for me. Player: Venore
Zebron: Aaaah, Venore, Venore, what a wonderful town. Especially for someone with love for gambling like me. Player: Hugo
Zebron: I had a cousin named hugo, why do you ask? Player: licence
Zebron: I don't care much for that law stuff, but as far as I know those Venore merchants got a royal gambling licence for the city. Player: bye
Zebron: Hey, you can't leave. Luck is smiling on you. I can feel it!