They Came From The Ultra Beyond

Stage 1: Freezington
Location: Freezington After completion of the other three Legendary Clue sections, if you have become Champion, then you will find a new Legendary Clue on the doormat of Peony's basecamp. This Legendary Clue. This clue provides very little details. A mysterious large hole that connects our world to another. This phenomenon was originally discovered by Professor Mohn. The hole connects to worlds where Ultra Beasts live. These are beasts that are different from the Pokémon that we are familiar with
Stage 2: Max Lair
Location: Max Lair If you take the clue to Peony in the Max Lair, he will say he doesn't recognise it but suggests that you investigate further in this quest. Soon after, a few trainers exit the Max Lair saying about mysterious Pokémon that have entered. The scientists note that this may be connected to the Ultra Wormhole that recently opened.
Stage 3: Max Lair
Location: Max Lair As you go through Dynamax Adventures, you will eventually encounter Necrozma. If you manage to catch Necrozma and show it to Peony, he will say you have investigated the mystery sufficiently and say that the task is now complete The scientist will come and say that they are her notes and she doesn't know how Peony got hold of them. She will give you a Beast Ball and an Ability Patch as thanks.

Complete Clue