Esmar Tuek was a spice smuggler during the time of Muad'Dib.
Tuek's operation was based in the polar regions of Arrakis. For many years he was responsible for smuggling spice off Arrakis for profit. A cunning and astute businessman, Tuek had secret arrangements with the Fremen, both as a means of making profit and as a way of undermining the rule of the Harkonnens.
When the Harkonnens were replaced by the Atreides on the order of the Emperor, Duke Leto Atreides convinced Tuek and his band of smugglers that House Atreides would ignore their operations if they gave a percentage of their profits to the Duke. Shortly thereafter, when Harkonnen spies tried to sell a stolen Atreides carryall to the smugglers, Tuek's men, under orders from Tuek, handed the spies and the carryall to Atreides authorities, earning Tuek the Duke's gratitude, as well as an invitation to a formal dinner hosted by the Duke and the Lady Jessica.
When House Atreides was attacked and the Duke killed, Tuek was killed, and Gurney Halleck, Atreides Warmaster, along with a handful of House Atreides forces, managed to escape and fall in with Tuek's son Staban and his men, where they remained for two years.
Tuek's descendants seemed to have remained on Arrakis. A distant yet direct descendant, Hedley Tuek was High Priest of the Rakian Priesthood some 5000 years after the time of Esmar Tuek.