Legendary trio

The legendary Trio are the legendary Pokemon Articuno, Moltres, and Zapdos.

Articuno is found in Seafom Island while holding Articuno Feather or in Water Temple while walking

Moltres is found in Mt. Ember and Mt.Silver while holding Moltres Feather

Zapdos is found in Power Plant Basement while holding Zapdos Feather

All 3 can be obtained from Cherish Ball

They are encountered as Level 85 so be prepared