Kingdom Protista: Amoeba

During unfavourable conditions such as drought, extreme temperature or lack of food, Amoeba withdraws its pseudopodia, becomes rounded and secretes a thick, protective three-layered cyst wall around itself. This is encystment.
Inside the cyst it can survive for a long time; it may also divide by multiple fission (sporulation) to form many pseudopodiospores.
When favourable conditions return, the cyst wall breaks and the young amoebae are released.
So the chief advantage of encystment is the ability to survive during adverse physical conditions.