How or where do you catch cobalion in Pokemon black 2 after beating the elite four i actually defeated twice and went to route 13 supposed be but not there?

You're right, Cobalion isn't found on Route 13 after beating the Elite Four. Cobalion is part of the Swords of Justice, a trio of legendary Pokémon that can be found after completing the main game in Pokemon Black 2 and White 2. Here's the breakdown of how to find and capture Cobalion:

1. Complete the Main Story: You need to have defeated the Elite Four and become the Champion.

2. Visit the "Hidden Grotto": This is a special location that appears randomly in the game. It's crucial you check every route that has a Hidden Grotto symbol on your map after completing the main game.

3. Look for Cobalion's Clues: Within the Hidden Grotto, you'll find clues that point to where Cobalion is currently located. These clues will be written in a special language. You can learn to read them by talking to specific NPCs in various locations.

4. Find Cobalion: Once you decipher the clues, they'll lead you to a specific location in the game, where you'll encounter Cobalion.

5. Prepare for a Battle: Cobalion is a powerful Pokémon, so be sure to prepare a team with strong Pokémon and appropriate moves.

Important Notes:

* Hidden Grottos are randomized: The location of Cobalion changes each time you play, so you'll need to keep checking them.

* Multiple attempts may be needed: It might take multiple tries before you encounter Cobalion in a Hidden Grotto.

* The Swords of Justice can be caught in any order: You can catch Cobalion, Terrakion, or Virizion first. Each has its own unique set of clues.

Remember, finding legendary Pokémon in Pokémon games is a part of the fun, so keep exploring the world and uncovering those clues! Good luck catching Cobalion!