Where can you find thunderous in Pokemon white 2?

In Pokémon White 2, Thunderous can be found in the Abundant Shrine after you have defeated the Elite Four and become the Champion. You will need to have the ability to access the shrine by using the event that involves the Pokémon Tornadus, which can be found in Pokémon Black 2. After you have Tornadus, return to the shrine, and Thunderous will appear for you to battle and catch.