Golduck's Soak changes the original type Pokémon to water type Pokémon; Soak cannot affect Arceus. My Serperior's Giga Drain and Leaf Blade is effective to defeat the Elite Four's Pokémon if Elite Four's Pokémon is previously soaked (except if Elite Four's Pokémon is Golurk and Krookodile which can be defeated with Golduck and Serperior without soaking).

With none of these really,and I forgot my pokemon..