Duraludon is a new Dragon-type Pokémon in Sword and Shield. It is an attractive Pokémon for serious trainers for a couple of reasons. Duraludon has excellent base stats, making it perfect for battles, and can also have the Dynamax ability.
You can find Duraludon on Route 10, outside of Wyndon. It will spawn between levels 45 and 48, but only has a one percent chance of spawning in overworlds. Route 10 is just before taking on the Champion's Cup, making Duraludon a great addition to your squad if you can catch him.
If you wish, you can also visit Outrage Lake in the wilderness area, which is a hotbed of powerful Pokémon spawns. The problem here is that so many different Pokémon spawn in this area that it's a bit of a fluke, and the ever-changing climate can make plans to catch a particular moot Pokémon.
Duraludon has a two percent chance of spawning in this area during heavy snow, and it's a hidden encounter, making it awkward because you'll have to start the Battle to see what kind of Pokémon it spawned. If you are in the wilderness, you can change the weather to increase the chances of catching this Pokémon.
The last places you might come across this mighty Pokémon are in Raid Max Battles, or potentially as a strong Spawn in the wilderness. Again, the possibility of this is slim. With spawn rates this low, it almost makes sense to make your hunt for Duraludon a secondary objective while doing other things in these areas or hunting for other Pokémon. The good thing about trying Max Raid Battles is that it might give you a Duraludon that can Gigantimax.