Tapp was a dungeon guard in Michina during the ancient times. He guarded the cell that Damos, Ash, Dawn and Brock were kept in. He didn't believe Damos was a bad person but he was under orders from Marcus to watch them.
When Pichu arrived with the key to the cell, Tapp didn't do anything to stop Damos and Ash from escaping. He followed them into the main hall to see what was happening.