In addition to new movesets for most Pokemon, as well as a number of New Pokemon altogether, Pokemon Ultra Sun also introduces a number of new Evolution Methods. Some of these Evolutions rest solely in a certain Pokemon learning a given move and then leveling up with said move, others require to have a certain ability and a specific time in order to evolve, and even some must be in a specific location in order to reach the next stage in their chain.
New Attack Based Evolutions
Poipole is one of the newest Ultra Beasts found in the World of Pokemon. What makes Poipole all the more unique is that it is the only known Ultra Beast that can evolve. In order for Poipole to evolve into Naganadel, Poipole must Level Up while knowing the move Dragon Pulse.
New Ability/Time Based Evolutions
Apart from Pikachu and Necrozma having brand new Forms in Pokemon Ultra Sun, Lycanroc also receives a new form called its Dusk Form. In order to evolve Rockruff into Dusk Lycanroc, Rockruff must have the ability of Own Tempo, be at Level 25 or greater, and must be evolving between 5-6PM. It's a lot for one given evolution, but it will be well worth it in the end!
New Location Based Evolutions
Back in Pokemon Sun & Moon, players couldn't evolve certain Pokemon that received Alolan Forms into their regular Kantonian Forms. Instead, players would have to transfer Pokemon from previous Generations in order to acquire said Kantonian Forms. However, that has all changed in Pokemon Ultra Sun, now that these given Pokemon can evolve into their Kantonian Forms in Ultra Space. Pikachu can evolve into a Kantonian Raichu by using the Thunder Stone in Ultra Space, Exeggcute can evolve into Kantonian Exeggutor by using the Leaf Stone in Ultra Space, and Cubone can evolve into Kantonian Marowak at Level 28 in ultra Space. Other Pokemon, such as Magneton (Magnezone) and Charjabug (Vikavolt), can evolve into their Final Evolutions by leveing up on Brush Mountain.