Drill Eggman II (ドリルエッグマンII), also known as Egg Digger, is the sixth boss of Sonic the Hedgehog 2, appearing at the end of Mystic Cave Zone.
Dr. Eggman is in another drill-mounted Egg Mobile, now outfitted with two drills which he will actually use to burrow through the ceiling of the cave. Upon emerging from the ceiling, he will point the drills forward and drive forward a little ways, then he'll rise up and drill through the ceiling. Upon doing this, Eggman unleashes a storm of debris that will rain down from the ceiling. While the rocks are harmless, the stalactites that fall with them are harmful. The player should simply avoid the stalactites and hit Eggman when he descends from the ceiling.
After eight hits, the mech will be destroyed, and the player will escape the caves and reach Oil Ocean Zone.