These gears are broken. If you insert a Chaos Emerald into each gear, its power may be able to repair it.
— Description, Sonic Generations (Console/PC)
The Lair of the Time Eater is a location that appears in the console/PC version of Sonic Generations. It is a hidden location within White Space where the player can repair special temporal gears and unlock the entrance to the Time Eater's dimension.
The Lair of the Time Eater is composed of countless gears and clockwork parts floating in midair, with black walls and floors enclosing the general area. In the foreground are seven golden gears, each one with incrementally smaller platforms, and in the far right end is the portal to the Time Eater's dimension.
In gameplay, the Lair of the Time Eater can first be visited after beating the Egg Dragoon. At first, there are seven fractured golden gears and the portal to the Time Eater's dimension is closed. The player's objective is to repair the gears using the Chaos Emeralds. While it is never said how the Chaos Emeralds are related to those gears, it appears that the Emeralds' power are suitable for repairing them.
Every gear in the lair can be activated by simply approaching them. An Emerald will then float into the center of the gear, causing it to reassemble itself and start to turn (the gears can be restored in any order). The player can then use the platforms attached to the gears to reach the next gear. When all the Chaos Emeralds have been inserted, the portal to the Time Eater's dimension will rotate and its torches will be lit one by one. When all twelve flames are ignited, the portal opens and the Chaos Emeralds will return to Sonic, allowing the player access to the final boss.