Lorelei owned a Cloyster in all main Pokémon games. It debuted in Pokémon Red and Green, being at Lv. 53 and knowing Supersonic, Spike Cannon, Clamp and Aurora Beam.
Prima used Cloyster to battle a trainer during her lecture. Afterwards, she used it to battle Pikachu, who did not manage to get a lot of chances to attack Cloyster. After Pikachu hit Cloyster with a Thunderbolt, Cloyster retaliated using Rage, defeating Pikachu with an Aurora Beam and a Take Down attack.
Lorelei used Cloyster and Dewgong to make an ice spike to attack Yellow and Bill.