Pokemon Sword and Shield's Galar forms bring new life to old Pokemon designs and - as is the case with Galarian Linoone and Obstagoon - occasionally even add entirely new evolutions to existing Pokemon families. Obtaining these Pokemon can require some extra work, however, as Obstagoon is one of many Sword and Shield Pokemon with unique evolution requirements.
Game Freak has been giving Pokemon special evolution techniques since Pokemon Red and Blue, with certain monsters requiring elemental evolution stone items to evolve or only evolving when traded. The developer has gradually amped up the complication factor with each generation, making some Pokemon nearly impossible to catch without a walkthrough. Many Pokemon require players to boost stat values they can't even see in-game in order to evolve, such as Feebas, the ugly Generation III fish Pokemon that only evolves once its hidden Beauty stat is raised. Other evolution steps, like those required to evolve Galarian Yamask, take things to the next level. In Yamask's case, players need to make the Pokemon take a certain amount of damage without dying and then take it to a particular spot in the Wild Area, all without a single indication in-game. While evolving Galarian Linoone is nowhere near as complicated as these obtuse evolution examples, players would likely only successfully do so on accident if they hadn't looked it up.
Getting a Galarian Linoone in the first place is fairly simple. Galarian Zigzagoon, the evolution stage before Linoone, can be found all over the place in the games' first few routes and in certain parts of Pokemon Sword and Shield's Wild Area. A good place to find them is the Bridge Field zone, located beneath the large stone bridges in the northern half of the Wild Area (see the map below). Galarian Zigzagoon will automatically evolve into Galarian Linoone once it reaches level 20. To make things a bit easier, players can instead occasionally find and catch Galarian Linoone itself in the Wild Area. One is usually found out in the open (away from the tall grass) in the Bridge Field Wild Area zone.
Once players have Galarian Linoone, transforming it into Obstagoon requires only two steps: First, Galarian Linoone must reach at least level 34. This can be accomplished simply by having it in the player's party while other Pokemon battle, but some quicker ways to boost its experience are to feed it high-level Pokemon Camp curry or give it experience-boosting Candy items, found regularly after beating Max Raid Battles.
Second, once Galarian Linoone reaches level 34, players need to level it up one more time. But, like the new Ice/Bug type Pokemon, Snom, Galarian Linoone will only evolve if this is done after dark. Galarian Linoone turns into Obstagoon if it is reaches level 35 or higher at night. No matter what time the Nintendo Switch's internal clock says it is, Pokemon Sword and Shield only count a Pokemon as evolving "at night" if it's actually night in the area a player is in-game. This means that, until a player has beaten the games' story, causing routes and towns to begin following a real-time day/night cycle, the easiest way to get Obstagoon is to take Galarian Linoone to the Wild Area when it's dark out. (The Switch's internal clock can also be changed in the system settings to make this easier.) Once this is done, Obstagoon will be ready to rock like the metal-head it is.
Pokemon Sword and Shield released for the Nintendo Switch on November 15, 2019.