Ultra Space

Walkthrough: After going through the wormhole into Ultra Space, you and Lillie will have to travel through this alternate dimension by yourselves, as Solgaleo must remain where it's at to hold the portal open. As you and Lillie walk down the one and only path, you will eventually find Guzma off to the side, high up in a tree of sorts. He will explain how he has never been afraid of nothing, he's actually always been the one to fear others, but after trying to capture the Ultra Beast and it taking control of Guzma momentarily, he now knows what fear truly is. He will end by saying he thinks Lusamine is too far gone in her madness because of the Ultra Beasts.

As you reach the end of the path, you will discover Lusamine. Lillie will try to reason with her, telling her she still loves her mother and she forgives her for every thing that has happened, but not before first going off on her for being an absent parent in their youth. Lusamine will dismiss her words, saying she wasn't beautiful enough for her, now like her Ultra Beasts. At that specific moment, more Ultra Beasts will appear, and Lusamine will actually merge into one with Nihilego. It is then up to your trainer to Battle the hybrid between Pokemon and Human in order to try to save Lusamina from both herself and from the mind hold of the Ultra Beast. (All of Lusamine's Pokémon have got Stat boosts in various Stats: Clefable in Sp. Def, Mismagius in Speed, Lilligant in Special Attack, Milotic in Attack, Bewear in Defense. )

Aether President Lusamine - Level 50 Clefable, Level 50 Lilligant, Level 50 Mismagius, Level 50 Milotic, Level 50 Bewear

After defeating the hybrid of Lusamine, the Pokemon and Human will split again. As the Nihilego begin to disappear again, the Ultra Space portal will begin to close because of them too. Lusamine will be unconscious for a moment after the separation, her Body being very weak from what Nihilego absorbed, but awakes long enough to tell Lillie how beautiful she now appears to her. After which, Solgaleo will rush on the scene and the four of you (Guzma included in such) will escape Ultra Space back through the closing portal.