The Silver Castle Zone boss is the fifth boss fought in Sonic Blast. It is an Egg Mobile outfitted with two laser cannons on each of its sides.
Upon stepping onto the final teleporter in Act 3, Sonic or Knuckles will be transported into an arena that places them on top of a giant wheel, with two diagonally-aligned mirrors on each side of the wheel and a third mirror above the player. Dr. Eggman will be shown in his mech high above the arena. Not only is he too high to reach, but an invisible barrier will prevent Sonic or Knuckles from reaching him.
Eggman will activate one of the laser cannons mounted onto his Egg Mobile and fire a laser directly downwards onto one of the mirrors on the sides of the arena, which will then bounce off the mirror and towards the player. To avoid these lasers, the player has to jump over them. Afterwards, the camera will pan back up to Eggman as he fires another laser. In order to damage the mech, the player has to run along on the wheel to move the third mirror and try to intercept the laser, reflecting it back at Eggman. Running towards the left will move the mirror to the right, and vice versa. From time to time, Eggman may attempt to fake out the player by attempting to charge one of the laser cannons, then deactivate it and start up the other one.
To defeat the boss, the player has to reflect thirteen lasers back at the boss. After the boss is defeated, what happens next is determined whether or not the player has collected all five Chaos Emeralds. If they haven't collected them all, the game will end and display the bad ending where the Silver Castle sinks into the ocean with Eggman making his escape. If they have, the player will move on to the true final boss.