Sonic Underground: Secrets of the Chaos Emerald

Secrets of the Chaos Emerald focuses on Sonic, Manic and Sonia as they help Knuckles, Floating Island's stern guardian of the Chaos Emerald, protect the Chaos Emerald from Dr. Robotnik and his henchmen, Sleet and Dingo. If the Chaos Emerald gets into the wrong hands it can be used as a weapon against Sonic and Mobius, but at the same time the Chaos Emerald can be used to save Mobius - there has never been so much pressure on Sonic and his siblings.

Sonic Underground: The Queen Aleena Chronicles

The Queen Aleena Chronicles is centered around one thing: Queen Aleena. Dr. Robotnik is out to conquer Mobius, what else is new, and some of his plans include: marrying the Queen, kidnapping the Queen, stealing the Queen's crown jewel, and unbalancing the peace in the valley of Mobius. It's, of course, up to Sonic and his siblings to stop Robotnik while using the power of music to settle all their feuds.