When the children and the Gym Leaders, including Olympia, found the Ultimate Weapon in Geosenge Town, they tried to seal it. Olympia had Slowking attack the weapon to prevent its activation. After the Ultimate Weapon had been activated, Olympia had Slowking create a barrier, along with her Meowstic and Valerie's Mr. Mime.
After the battle was over, Olympia sent Slowking to help rescue people and Pokémon that were affected by the Ultimate Weapon's blast.
None of Slowking's moves are known.