Dialga is a dual-type Steel/Dragon Legendary Pokémon introduced in Generation IV.
While he does not evolve into or from any other Pokémon, Dialga transforms into a second form, called his Origin Forme, while holding an Adamant Crystal.
Along with Palkia, Giratina, and their creator Arceus, he is a member of the Pokémon of Myth, representing time. In the past, he was worshipped by the Diamond Clan under the name "almighty Sinnoh" (a name actually referring to Arceus).