Only in Ultra Sun
Gift: Heahea Beach
You won't find Marowak in the wild in this game — you get it as a gift or by evolving Cubone (Level 28).
For the look, the best colour match is Nest Ball or Safari Ball.
Evolution: Cubone → Marowak (Level 28).
Marowak in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)