World Entrance Level 2 is the final boss battle of Knuckles' Chaotix. The boss battle is against a huge, red version of Metal Sonic, with a slightly elongated, cat-like face.
After losing to the player, Metal Sonic comes to Dr. Robotnik. With his Special Ring, the Doctor motions Metal Sonic and escapes. Suddenly, through an apparent transformation that occurred off-screen (although this is unconfirmed), Metal Sonic or a monstrosity based on him seems to appear as a huge, red, cat-like mechanical being, and the character (whichever the player chooses) and his partner fall into a square room with ten Rings in hand to fight it.
Regardless, it must be defeated in phases because of its large size. During the first section, hit the body eight times to destroy the left hand and the final boss will go into the background and attempt to hit the player with his right hand. After another eight hits, its right hand will be destroyed and the robot will go to the left of the arena and will fire a huge laser, which can be dodged by ducking. After eight hits, the robot will be defeated. If the player has all six Chaos Rings, the good ending will play with the Rings disappearing and Sonic and Tails appearing in the Tornado behind the Chaotix Crew (Sonic and Tails' only appearance in the game). If the player fails to collect the Chaos Rings, the final boss will appear overlooking a city burning in flames (possibly Newtrogic High Zone).
This fight can be very easy if playing as Charmy and Heavy, as Charmy is invincible while flying and Heavy is invincible in general.
In the Sonic the Hedgehog comic series and its spin-offs published by Archie Comics, the World Entrance Level 2 boss is referred to as Titan Metal, and is a name given to several incarnations of the character. The first Titan Metal Sonic that appeared was a transformation of Metal Sonic v2.0 which he achieved with a Power Gem. However, he was defeated by Knuckles. The next incarnation to appear would be a rebuilt model made by Dr. Eggman as the ultimate attack robot, which he would begin deploying in the aftermath of Operation: Clean Sweep.
Following the events of the Super Genesis Wave, the history of Titan Metal Sonic is presumable the same as its game counterpart.
This unnamed boss is apparently Metal Sonic's first transformed incarnation. Fleetway Editions imagines it as a separate robot character, whereas Archie Comics considers it a transformation - the original game itself is unclear.
By hacking into Knuckles' Chaotix, it is possible to find an unused sprite of the head of the boss with several tubes hanging from the "neck". This could have been used as part of its escape sequence should the player fail to collect all the Chaos Rings.