The Egg Golem (エッグゴーレム,Eggugōremu?) is a boss in Sonic & Knuckles, as well as its locked-on form. It is fought at the end of Sandopolis Zone Act 2. 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 sphinx constructed around an Egg Mobile within 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 the Egg Mobile, which is hidden away beneath a layer of stone tiles. It constantly moves forward and charges the laser on the front of its head at regular intervals, which fires a white beam at a 45 degree angle down to where the player will likely be standing.
The player must hit the head of the Golem, which is the only weak point on its body. This causes the stone tiles protecting Robotnik/EggRobo to recede, providing a window of about two seconds to hit the now-revealed Egg Mobile before the tiles cover it up again. Eight hits are required to defeat the boss. The left arm acts as a stepping stone that the player can use to jump up and hit its head (which is especially useful for Knuckles, who has a lower jump height than Sonic and Tails), but the player must be mindful of the spikes that cover most of the Golem.
This boss must be completed in a certain amount of time as eventually Sonic, Tails, or Knuckles will 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 Egg Golem moves forward about twice as quickly as it does for Sonic and/or Tails, giving the player less time to defeat it. If it gets close enough to the wall, Knuckles can climb the wall and glide into the Egg Golem's head.
If the Egg Golem makes it to the wall and does not crush the player due to being in Debug mode, it will backpedal back across the room very rapidly before moving forward again and repeating the process.