Drinkmaster Tahnu appears in the quest The Drunken Master and attacks your party when you approach him. He will quickly become allied to you if you don't kill him first. After allying with you he will walk towards Kaineng Center and will die at the gate.
If you follow him to the entrance of Kaineng Center, he will die. Warriors can capture the elite from him, as he is technically a dead boss. However, he has a tendency to get caught on a group of NPCs, which halts his progress completely and prevents his "death," so this is not a very reliable cap. However, it is possible to body-block him along the way to steer him past the clump of intervening NPCs. The same skill can be acquired more reliably from Afflicted Guardsman Chun during The Afflicted Guard.