From Bulbapedia, the community-driven Pokémon encyclopedia.
Trest (Japanese: ダグデ Dagde), often referred to as the Mayor, is a key non-player character in Pokémon XD. He lives and works in Phenac City, in Orre. He has assumed the job of Mayor from Es Cade.
The player's first trip to Phenac City is to inform the Mayor of Cipher's upcoming attack. His home is found empty except for a woman who is apparently his secretary. She will not allow the player to explore the house until she is distracted by playing the Music Disc on the stereo in the room. Upstairs is the Mayor's Note lying on the floor next to the Mayor's bed; it is a warning to Justy of Cipher's plan, suddenly interrupted by the 'secretary,' who is actually a Cipher Peon.
Following the defeat of Snattle and the other Cipher agents in the city, the player acquires an Elevator Key to reach Pre Gym's basement. There, the Mayor is finally found, being held hostage with the rest of the citizens. If the player visits him at his home following his rescue, they will be rewarded with an Exp. Share.
Trest often patronizes Realgam Tower and will send the player an e-mail when it reopens during the game.