Early in Sonic Adventure 2, Knuckles and Rouge argue over the Emerald; she wants the pieces for her personal collection. Eggman tries to steal it, so Knuckles shatters it aboard Eggman's hovercraft, sending the pieces every which way. He spends the game recollecting the pieces similarly to in Adventure. He later helps Sonic, Tails, and Amy find Eggman's base inside a giant pyramid, as well as a key to an inner chamber housing a giant space shuttle. He follows them to a giant space station called the ARK with it, where he again scuffles with Rouge over the Emerald. He saves her from falling into a constructed pit of lava; she decides the shards are worthless and dismissively lets him keep them, so he reassembles the Emerald and runs off. The game's antagonist Gerald Robotnik, Eggman's grandfather, initiates a program to send the ARK on a collision course with Earth as revenge for an attack on the ARK decades earlier, so Knuckles teams up with the other playable characters to reroute it.