Burned Tower Suicune .

One of the legendary beasts that roams Johto. Legend has it, that it's presence can instantly purify filthy, murky water.

In Pokémon HeartGold & SoulSilver, Suicune will traverse across Johto and Kanto, before finally allowing the player to battle with it.
If defeated previously, it will respawn at Burned Tower after the player defeats the Elite Four again.