Ash's Lycanroc (Forever)

Ash's Lycanroc is the second Pokémon Ash obtained in the Alola region.

Under Professor Kukui's care
Rockruff was a wild Pokémon that one day stumbled across Professor Kukui's house. It was starving and left confused from another Pokémon's Teeter Dance. Professor Kukui gave it some Pokémon food, which made Rockruff decide to stay at Kukui's house. From then on, Rockruff lived with Kukui, although he never caught it in a Poké Ball.

With Ash
TBA

Personality and characteristics
Rockruff is a playful, affectionate Pokémon that gets along well with both Ash and its previous caretaker, Professor Kukui. The first night Ash stayed with the Professor, Rockruff, Pikachu, and Ash were quickly able to befriend each other. Like other members of its species, Rockruff likes to greet and show affection to others by rubbing up against them with the rocks on its neck, although it doesn't seem to be aware that it stings the recipient.

Although Rockruff lived with Professor Kukui before being caught by Ash, it was actually a wild Pokémon that Professor Kukui was taking care of. When Ash revealed this to his classmates at the Pokémon School, his Rotom Pokédex added that Rockruff readily bond with humans even if they are not captured by a Trainer.

Rockruff has been shown to have a strong sense of smell which has been used to help find Rowlet and Popplio, Ash's missing Electrium Z and DJ Leo's Dugtrio.

Though generally friendly, Rockruff is prone to becoming hotheaded when faced with a challenge it wishes to overcome despite what risks it might project itself to. During Olivia's Grand Trial, Rockruff was uncharacteristically aggressive towards others, doing things like biting Ash multiple times, trying to rile up Olivia's Lycanroc and knocking out Rowlet when it attempted to lift it up into the air. The latter incident caused Rockruff to snap back into reality after noticing what it had done and become remorseful. Following her defeat, Olivia pointed out to Ash that Rockruff's temperament was a sign that it was about to evolve.

Trivia

 * Lycanroc is Ash's first Alola Pokémon to fully evolve.