You must first place the Odd Keystone in the Hallowed Tower. Then you must meet 30 different people in the Underground. Afterwards, a Spiritomb should appear at the Hallowed Tower. Save in front of it and talk to it. If it is not shiny, then keep reseting your game until it is.
Chat with our AI personalities
i think you have to trade for it
You can't catch shiny legendary Pokemon without cheats... sorry
You don't, it is used to catch spiritomb after meeting 36 people underground
It takes luck to come across a shiny, but when you find one you catch it like you would catch a regular Pokemon.
No they programmed the game so you can't catch shiny victini, reshiram, and zekrom. All other pokemon can be found shiny.