Pokémon Ultra Sun and Ultra Moon/Champion Title Defense

What's also new in Sun and Moon and Ultra Sun and Ultra Moon are "Champion Title Defenses". These replace the typical champion battle with other trainers trying to steal YOUR champion title. This new feature also is random and the player won't know who they're battling next until the trainer walks up the steps. The selection of trainers include:

1. Hau

 * Occupation: Your Rival
 * Pokemon: Alolan Raichu (Level 69), Noivern, Tauros (Both Level 68), Crabominable (Level 69), Flareon/Leafeon/Vaporeon (Level 68), and Primarina/Incineroar/Decidueye (Level 70)

2. Lusamine

 * Occupation: Aether Foundation President
 * Pokemon: Clefable, Lilligant , Milotic , Bewear , and Lopunny (All Level 68).

3. Guzma

 * Occupation: Team Skull Leader
 * Pokemon: Golisopod, Masquerain, Pinsir, Vikavolt, and Scizor (All Level 68).

4. Plumeria

 * Occupation: Team Skull Admin
 * Pokemon: Gengar, Crobat, Toxapex, Salazzle, and Muk (All Level 67)

5. Kukui

 * Occpuation: Pokemon Professor
 * Pokemon: Lycanroc (Midday Form and Level 69), Incineroar/Primarina/Decidueye, Magnezone, Braviary, Alolan Ninetales, and Snorlax (All Level 68)

6. Hapu

 * Occupation: Kahuna
 * Pokemon: Golurk, Flygon, Gastrodon, Krookodile (All Level 68), and Mudsdale (Level 69).

7. Tristan

 * Occupation: Youngster
 * Pokemon: Emolga, Tauros, Sharpedo, Magmortar, and Alolan Exeggutor (All Level 66).

8. Ryuki

 * Occupation: Dragon Expert
 * Pokemon: Garchomp, Drampa, Dragonite, Turtonator, and Kommo-o (All Level 67).

9. Sophocles

 * Occupation: Trail Captain
 * Pokemon: Togedemaru, Golem, Electivire, Vikavolt, and Magenezone (All level 67).

No Gladion?
You were able to battle against Gladion in Pokemon Sun and Moon however in Ultra Sun and Ultra Moon, he was seen leaving the island to travel to Kanto and Johto, but can be faced 1 month after you have beaten necrozma.