Cannon's Core is the final level of Sonic Adventure 2 and the first to have all the players playable. It takes place inside the Eclipse Cannon with the Dark and Hero characters have to stop the Chaos Emeralds.
Eggman implants the Yellow Chaos Emerald in the Eclipse Cannon and it makes the Space Colony ARK fall to Earth. After Rouge reads Gerald Robotnik's Diary, they all come up with a plan to use the Master Emerald to stop the Chaos Emeralds.
Tails in the Cyclone and Eggman in the Egg Walker must destroy the security doors to let the others reach the chamber above the Eclipse Cannon. Next, Rouge must drain the liquid from the Core so Knuckles can open the final security door. As Knuckles, swim to the switch and push it to let Sonic the Hedgehog proceed to the core. Amy then convinces Shadow to save the planet. He then helps Sonic and Knuckles stop the Chaos Emeralds by distracting the Biolizard.
After Shadow defeats the Biolizard, Knuckles drains the Chaos Emeralds of their power, but the Biolizard absorbs the Chaos Energy and uses Chaos Control to warp outside and keep the ARK on it's crash course, transforming into the FinalHazard. Sonic and Shadow then transform into Super Sonic and Super Shadow and destroy the FinalHazard.
Shadow dies and Sonic brings his limiter rings to Rouge and they head back to Earth with Sonic saying goodbye to Shadow.
It is similar to the stages on Space Colony ARK. This level features switches that freeze time, which are useful for they can also freeze the clock for an easy A rank, and can be used infinitely. The switches also freeze waterfalls, acid pits, and fast-flowing water, so they can be walked on; however, the switches only last about 10 seconds, and a beep will start to sound, when it starts to be repeated pretty fast, it's about to end, so you must be careful. In Sonic's level, it reassembles the Pyramid Cave level. In the boss battle with the FinalHazard, it is aerial in space.