The Plate of the Lakes Mission Walkthrough - Pokemon Legends: Arceus
Travel to the Obsidian fieldlands and fly to Lake Verity.
Go inside the cave. Capture the Lv70 Mesprit.
Next, go to the Mirelands. Then, head to Lake of Valor.
You must enter the cave and capture the Lv70 Azelf.
And finally, go to Alabasta and head straight for Lake Acuity.
Go inside the cave and capture the Lv70 Uxie.
After catching the Lake Trio, you'll win the Draco Plate and complete the mission.