From Sonic Retro
|Twenty-third level, Sonic Forces|
|Location: Eggman Empire Fortress|
|Level theme: industrial|
|Played as: Classic Sonic|
| Non-English names:|
|← Mortar Canyon | Final Judgement →|
Iron Fortress is the twenty-third stage of Sonic Forces and the fifth stage to be played by Classic Sonic. The stage is located inside the Eggman Empire Fortress and leads through the lower sections of the fortress.
With Infinite's demise, his Phantom Ruby has left him and headed underground, making Tails suspect that Dr. Eggman may be up to something. As such, he tells Classic Sonic to find an entrance into the Eggman Empire Fortress's Central Tower so they can stop whatever Eggman is cooking up.
Although other search parties are on the job as well, they have no luck finding an entrance, much to Silver's disappointment. Knuckles, on the other hand, is willing to bet that the area Classic Sonic is searching is holding what they are looking for. Sure enough, Classic Sonic proves Knuckles' hunch to be correct by finding a secret passage for reinforcements to infiltrate the tower with.
As the final Classic Sonic stage, this 2.5D stage is filled with all manner of treacherous hazards such as Missile Pods that fire missiles at the player, electrical fields that inflict damage upon touch, and spiked balls that move around in patterns. Many of the platforms also have a tendency to fall, so the player must watch their step. Also dotted around the level are flywheels like those seen in Scrap Brain Zone and Metallic Madness, which the player can climb and build up speed on.
Halfway through the stage, the player is thrust right into an auto-scrolling section reminiscent of levels such as Bridge Zone and Desert Ruins Zone 4. This section is a very challenging platforming segment that's abundant with bottomless pits and Missile Pods, all of which the player must avoid as they hop across platforms and flywheels. One mistake here can potentially lead to a fall.