Tails' mission is to navigate through ARK and find the colony's power generator and destroy it so that Sonic can place the fake Emerald in the Eclipse Cannon.
The primary gimmick in this level is that of dynamite hatches. Whereas in other stages, dynamite is used to perform useful demolitions, shooting dynamite in this stage results in the creation of a vacuum field that attempts to suck Tails out into space from close range, and succumbing to the field results in loss of life. The dynamite packs are also attached to platforms which make navigation much more difficult upon their destruction. Tails must avoid destroying these dynamite hatches. Tails also must destroy many G.U.N. enemies.
The best approach to completing this mission is to move as quickly as possible while still proceeding with caution. Precise use of Lock-On Missile is imperative. The player should be very careful not to cause an explosion and then walk right into it. If one stays along the main path and does not get hit, it is possible to collect 100 Rings in under 3:30.
Find the lost Chao
The first time it is possible to step outside after passing the first point marker, an Ancient Ruin can be found atop a floating platform. The player must fly over to this shrine and play the Mystic Melody. A series of stone blocks will then appear, leading to a metallic platform. This platform can elevate the player to another stone block, from which the player must hover onto another metallic platform moving from left to right. Once there, the player should wait for the platform to float as far as it can move in either direction before they can leap off and hover toward the door.
After passing through the door, the player should not shoot the Artificial Chaos inside the room, as doing so will cause every space hatch in the room to open. Instead, they must run past the Artificial Chaos and into the next room. The player should jump onto the cages and wait until the moving platform gets toward the middle, then jump to it. When the platform floats closest to the door, the player must jump and hover over the lasers, then go through the door to reach the lost Chao.
Reach the goal within 5:00
Time is tight in this stage, so the player has to move quickly. There are not any real shortcuts, so it is up to practicing to finish the stage in time.
Clear Hard mode
The only differences in this mission compared to the first mission are the number of enemies and the addition of more space hatches.
Chao Container locations
After the first Point Marker, the first Chao Container can be found among the Wooden Containers in the room with the Switch.
After the second Point Marker, the second Chao Container can be found among the Steel Containers on the right in the green energy fluid pit room.
After the third Point Marker, the Chao Container can be found behind the locked door, whose Switch is located outside the platform maze area.
After getting the BazookaLevel Up Item and going into the hallway afterward, Big can be seen beyond the third window on the left.
In the Biolizard report that Rouge supplied to Shadow in the dark story, an "eternal engine" was mentioned as working normally with the Biolizard. Whether there is a connection between the stage "Eternal Engine" and the Biolizard other than a similar name is not revealed.
The 2P Battle version for Eternal Engine is the battle arena Tails and Eggman use for their rematch, with the music playing being the same as said boss fight's music.