Sonic the Hedgehog 2
Sol, called Gola (ゴーラ) in the Japanese manual, is a badnik from the 16-bit version of Sonic the Hedgehog 2 found in Hill Top Zone. It carries four fireballs, which rotate around its body. When the player gets close, it fires them straight ahead. Sol can be defeated by ducking and waiting for it to release all four fireballs - it is then completely defenseless. Sol is similar in design to Orbinaut, a badnik from Sonic the Hedgehog.
A second Sol, known as Gola (ゴーラ) in the Japanese manual and by what it's mostly called, appears in Sonic Adventure. It's very close in design with the original from Sonic 2. It usually hovers around orbited by the cluster of flaming orbs and it attacks by expanding or contracting said cluster to adjust the position of the attack radius.
Sonic Adventure 2
Yet another Sol, known as Gola (ゴーラ) in the Japanese manual and by what it's mostly called, appears in Sonic Adventure 2. It's very close in design with the one present in Sonic Adventure, but it has four distinct fire balls, and though it has the same behaviour and attacks, once a fire ball hits an enemy, it will disappear. It awards 100 points when destroyed.