The Egg Golem (エッグゴーレム,Eggugōremu?) in Sonic & Knuckles (or Sonic the Hedgehog 3 & Knuckles) is the boss that is fought at the end of Sandopolis Zone (the third or ninth zone respectively). The battle is fought across a large, flat floor at the bottom of the pyramid that Act 2 takes place in.
The Egg Golem is a tall, stone machine constructed around an Egg Mobile in the torso. It is about seven times the height of Sonic the Hedgehog. It is clad in stone armor and has spikes on the front of its feet as well as on its torso. At the top there is a green gem resembling an eye, which acts as an energy weapon.
Dr. Robotnik (or EggRobo in Knuckles' case) pilots the Golem from within his Egg Mobile which is hidden away inside the stone armor. It constantly moves forward and at regular intervals charges the laser on the front of its head, which fires a white beam at a 45 degree angle down to where the player is likely to be standing.
The player must hit the head of the Golem, which is the only weak point on its body. This causes the armor to retract, providing a window of about two seconds to hit the newly-revealed Egg Mobile. Eight hits are required to defeat the boss. The left hand acts as a platform that the player can use to jump up and hit its head (especially useful for Knuckles) but the player has to be mindful of the spikes that cover most of the Golem.
This boss must be completed in a certain time as eventually Sonic, Tails, or Knuckles would be crushed between it and the wall at the other end of the arena, although, when playing as Sonic or Tails it is unlikely that this would happen before reaching the ten-minute limit (unless resuming from the Star Post having ran out of time once already). As usual, this boss is harder for Knuckles and the Golem moves forward about twice as quickly as it does for Sonic and/or Tails, allowing less time to defeat it.