Here's how you encounter him and the path you need to take:
1. Complete the Game: You need to finish the game, regardless of whether you choose the "Hero" or "Dark" path. The ending sequence will determine if you face Black Doom as an enemy or an ally.
2. The Final Battle: If you've completed the game and chosen the "Hero" path, Black Doom will be the final boss you face. You'll fight him on the planet "Black Comet" after battling through several levels.
Important Notes:
* The game's story is split into two paths: "Hero" and "Dark".
* Choosing the "Hero" path leads to a confrontation with Black Doom as the main antagonist.
* Choosing the "Dark" path leads to an alliance with Black Doom, and you'll fight alongside him against the GUN forces.
To access the final battle with Black Doom (as the antagonist):
1. Complete the game.
2. Choose the "Hero" path during gameplay.
3. Make sure to collect enough "Hero" emblems throughout the game to unlock the "Hero" ending.
Let me know if you have any other questions about Shadow the Hedgehog or any other game!