Egg Ball'n'Chain is the first boss of Sonic the Hedgehog O, fought in Green Hill Zone 2.
The Egg Ball'n'Chain is an egg-shaped floating sphere. Attached to it's bottom is a chain. On the end of the chain is a large, black wrecking ball.
The arena is a flat grassland with two platforms on the left and right.
Stay on the platforms. When the ball comes your way, jump at the Egg Ball'n'Chain and run to the other platform. Repeat until it dies.