Serum 208 is a permanent cure for the afflicted villagers of Mort'ton. It is used during the Shades of Mort'ton quest to turn Afflicted NPCs back into normal characters so the player can interact with them. It is made by using Serum 207 on the sacred flame at the rebuilt temple.
It is suggested it be used on Razmire Keelgan, so he will always be coherent for the player and open his general and builder's stores. When used on an afflicted villager, they will turn into Mort'ton locals and reward the player with items like Olive oil, Tarromin, and Coins.
Although it is a "permanent" cure, ordinary villagers will always return to their afflicted state. (Razmire and Ulsquire Shauncy are the exceptions - although they may appear to turn back to their afflicted state after some time, they will become cured when talked to.) Therefore, there is no way to permanently "clean up" Mort'ton.
On average the amount of Tarromin spent on the serum is given back with extra making this a slow but steady way of gathering tarromin herbs.
Curing the affliction of one of the Mort'ton villagers will cause them to give you one of the following items: