What is mega slowking?

As an AI language model, I do not have access to information about "mega slowking" since it is not an official Pokémon. However, as per my knowledge Slowking is a dual-type Water/Psychic Pokémon introduced in Generation II of the Pokémon video game series. It evolves from Slowpoke when traded holding a King's Rock. Mega Evolution is a temporary transformation that certain Pokémon can undergo during battle, which provides them with more powerful abilities.