Before I start talking about the video game, here's some stuff about the character.
In Sonic Heroes Shadow seeks his identity for he still has amnesia, with the help of his teammates he, Rouge and E-123 Omega form Team Dark. In 2006 Sonic the Hedgehog, he fought and defeated Mephiles, the Dark (is his nickname). But Mephilies managed to escape, and was able to join with Iblis, the Flames of Disaster to create Solaris, but Solaris was destroyed by (resurrected) Super Sonic, Super Shadow, and Super Silver.
Now, lets talk about the video game.
Could you believe that Sonic the Hedgehog is one of the bosses in this game?
The game features a 3-way war between ARK, the Black Arms, and Eggman. The player has to choose which side to take, like if you choose Dark, then you'll be a Black Arm solider, if you choose Neutral, then you'll work with ARK, and if you choose Hero, then it will be with, I think, the good guys, either that or you'll team up with Dr. Eggman.
In some point in levels you find a weapon for Shadow to use, in multiplayer mode these Android double-gangers can be playable characters, two of them have a built-in machine gun, two of them have a built-in bazooka, and two of them need to find a weapon just like the real Shadow.