Rockruff evolves into a different form of Lycanroc depending on the version of the game. If it evolves in Pokémon Sun, it will become the Midday Form; whereas if it evolves in Pokémon Moon, it will become the Midnight Form.
The midday form of Lycanroc tend to live in mountains. They are solitary hunters and actually avoid making packs at all costs to prevent disputes. However, to any trainer who accepted them while in their rambunctious Rockruff stage, they are fiercely loyal to a trainer they have bonded with.
The midnight form of Lycanroc prefers to let its enemy get the first hit before delivering a devastating counterattack. They are predisposed to violence and easy to get excited by a worthy opponent, which is shown by their glowing eyes. They will not accept trainers that they feel are poor battlers or give questionable orders.
Lycanroc is the evolved form of Rockruff, at level 25. Midday form is evolved during the daytime in Sun while Midnight form is evolved during the nighttime in Moon.
Rockruff's split evolution follows two common trends of small quadrupedal mammal Pokemon: some, such as Growlithe and Vulpix evolve in more "adult" but still animal-like quadrupedal forms, while others like Fennekin and Zorua become bipedal and anthropomorphic upon evolving. The Midday form follows the former, while the Midnight form follows the latter.
Midday form Lycanroc is based on wolves while Midnight form Lycanroc is based on werewolves.
Lycanroc is a combination of the words "Lycan" (from the Greek Lykos, meaning wolf) and Rock due to its typing. Lycan may also refer to the modern use of the word "Lycanthropy" (the technical term for the affliction of being a werewolf) due to how Rockruff evolves. The majestic, noble appearance of the Midday form in stark contrast to the Midnight form's sinister look may be a reference to wolves equally both being portrayed as benevolent as well as malevolent in culture.