Feist

Feist is a gigantic panda of unknown origin and power. He has black and white fur and green eyes. At some point, he was banished to the Zone of Silence, where he met and was defeated by Ixis Naugus. After Naugus escaped the Zone for the final time, Feist seized control and, using the power of all the galaxy's Chaos Emeralds, reshaped it into the Special Zone.

Prisoner in the Zone of Silence
Feist was first seen by Sonic when he entered King Maximillian Acorn's dreams while the king was comatose and succumbing to a crystallization spell set on him by Naugus. In the dream, Sonic learned that Feist attacked King Acorn shortly after his arrival in the Zone, but King Acorn escaped and eventually made an alliance with Ixis Naugus. Later, Naugus revealed that he had defeated Feist using his magic while battling Ultra Sonic and Hyper Tails. (StH: #43, #66)

Ruler of the Special Zone
Following the battle between Sonic the Hedgehog and A.D.A.M. and the transport of all Chaos Emeralds into the Zone of silence, Sonic and Tails traveled to the Zone in search of them. They found the dimension miraculously changed, Feist having fused the countless Emeralds into seven jewels and taken over. Apparently content with the Zone as his realm and considering the pair his loose allies due to their shared antagonism of Ixis Naugus, he granted them the grey Chaos Emerald, which was used to help King Acorn recover from poison. Feist stated that Sonic would have to earn the others if he wanted them, an event made all the more likely by the loss of the grey Chaos Emerald to Naugus' master, Mammoth Mogul. (StH: #169, #170, #186)

Background information
Originally, Feist's species was uncertain, some thinking he could be a badger or skunk, but he was later revealed to be a panda.