This is Cloyster's most effective set, and is the set that gave Cloyster its reputation as an incredibly dangerous sweeper. Shell Smash is the move that makes Cloyster so threatening; by doubling its offensive stats and Speed, it instantly becomes a threatening sweeper. Cloyster's main STAB attack, Icicle Spear, will consistently be 125 Base Power thanks to Skill Link, and after a Shell Smash, it will inflict massive damage on anything that doesn't resist it; even physical walls such as Ferrothorn and Skarmory take large amounts of damage. Rock Blast is an excellent coverage move, as not only is it boosted by Skill Link, it also provides great neutral coverage, hitting Fire- and Ice-types super effectively, and is Cloyster's main way of dealing with Talonflame, Gyarados, Volcarona, and Mega Charizard X. The fourth slot is based on personal choice. Hydro Pump is often the better option, as it allows Cloyster to break through physically defensive checks such as Skamory, Forretress, and Scizor with a bit of prior damage, while Razor Shell is Cloyster's best option against Assault Vest Tyranitar, Specially Defensive Jirachi, and Specially Defensive Heatran. However, Ice Shard can be used to KO a weakened Breloom, hit Talonflame before it attempts to revenge kill with Brave Bird, eliminate Choice Scarf Noivern and give Cloyster useful priority before it boosts, but it is often unnecessary.