Chaos Emerald (Sonic Underground)

The Chaos Emeralds are objects that appears in Sonic Underground. They are emeralds that hold destructive powers that, when unchecked, can destroy Mobius.

Description
The Chaos Emeralds are old single cut in shape, green and give off a bright green glow. They vary in size with Knuckles' emerald being large enough for both hands to carry while Dr. Robotniks emerald is small enough to be held in one hand.

The Emeralds powers are often use to keep large objects afloat, but the power can be used for defences and weaponry in the form of green energy. If a Chaos Emerald is destroyed the power can be apocalyptic to Mobius, such as wild energy storms and seizmic earthquakes.

History
The first Chaos Emerald was first introduced in "Friend or Foe?" and a second Chaos Emerald was introduced in the three-part Chaos Emerald Crisis.

Knuckles' Emerald
Knuckles is the guardian of the Chaos Emerald in the Floating Island. It's power is used to keep the island aloft in the sky. Dr. Robotnik sent Sleet and Dingo to trick Knuckles into believing Sonic Underground were the intruders while Sleet and dingo themselves were actually after the Chaos Emerald.

When Knuckles realised Sonic was not a theif he realised Sleet and Dingo were thieves from a Reflecting Pool. Knuckles worked with Sonic and his siblings to get back the chaos Emerald from Sleet and Dingo to prevent the Floating Island from crashing onto Mobius.

Dr. Robotniks Emerald
Dr. Robotnik aquired another Chaos Emerald which he used to power his Fortress of Altitude. Sonic tried to take the fortress down but after being chased by an emerald green energy field Sonic believed the fortress was powered by a Chaos Emerald and seeked Knuckles for help. Sleet and Dingo believed that their services will no longer be required by Dr. Robotnik and fearing termination and roboticization they stole the Chaos Emerald.

As Dingo and Sleet feud over who should rule Mobius, the Chaos Emerald ended up broken releasing it's destructive power onto Mobius. Aware of the chaos around them, the heroes go to see Great-grandfather Althair who entrust Knuckles with a canister and advice Sonic to make an alliance with Robotnik.

In order to secure the emeralds unstable power, Sleet turned Dingo into a safe, but the power was too much, turning Dingo into Chaos Dingo. With Chaos Dingo now a threat to Mobius, the heroes agreed to work together with Dr. Robotnik in order to trip Chaos Dingo up to fall onto Robotnik, having him spit out the emeralds. Knuckles put the pieces of the emerald into the canister, thus restoring Mobius to normal.

Trivia

 * Despite being the Chaos Emeralds of the Sonic Underground series, they bare apperances and powers more similar to the Master Emerald. Both emeralds are green and fairly large and their primary use is to keep large mass airborn.