Forget trying to get shiny legendaries, I'd rather waste my time getting a shiny of something I'd use. (unless it's Rayquaza. Shiny Rayquaza is worth it.)
some nice japanese person made a base where their pokemon team is 3 lv. 100 blisseys and it has a level release so you can fight them at lv.100, otherwise, they would be lv.50
some nice japanese person made a base where their pokemon team is 3 lv. 100 blisseys and it has a level release so you can fight them at lv.100, otherwise, they would be lv.50