Ultra Deep Sea

Ultra Deep Sea it's one of the several worlds of Ultra Space acessible though Rarity 1 White Warp Holes after defeating Necrozma, it's the home of Nihilego. In Pokémon Sun and Moon, after Nebby evolves into Solgaleo or Lunala, it takes the player and Lillie to Ultra Deep Sea (named Ultra Space) where Lusamine is faced for the last time.It is the home of the Ultra Beasts and its the local what Lusamine is faced for the last time.

Geography
Ultra Deep Sea is a dark cave with a dark stone path wich ends in a dead end with a small rock where the player can sit and several multicolored rocks resembling diamonds in the walls, several Nihilego are seen floating around the area.

Pokémon Sun and Moon
The player battles Lusamine after her fusion with a Nihilego. After the player defeating Lusamine, it's impossible to return to Ultra Deep Sea.

All her Pokémon have auras that boost the following stats by one stage:
 * Special Defense (Clefable)
 * Special Attack (Lilligant)
 * Speed (Mismagius)
 * Attack (Milotic)
 * Defense (Bewear)

Pokémon
A Nihilego is found at each visit in Ultra Deep Sea. It has an aura who boost it's Special Defense in two stages.

Trivia

 * In Pokémon Sun and Moon, the Rotom Pokédex doesn't work in the Ultra Deep Sea. In Pokémon Ultra Sun and Ultra Moon, Rotom always displays the Altar of the Sunne/Altar of the Moone minimap.
 * All of Lusamine's Pokémon have (except Bewear) an angry expression instead of the normal expression.
 * If an Egg is hatched in the Ultra Deep Sea in Pokémon Sun and Moon, the local where it is hatched will say Ultra Space.