Kingdom Valley

Flame Core is the ruins level in Sonic the Hedgehog. It is towards the North-East of Soleanna and once housed the King's of Soleanna. In everyone's stories Flame Core is inhabited by Dr. Eggman. Kingdom Valley is abound with water so the ancient ruins and weak wood aren't probably the best footholds.

Sonic
In Sonic's story, he is in pursuit of the Egg Carrier. Sonics Kingdom Valley is considered to be the hardest. It utilises a High-Speed area at the end of the level which takes place in a set of ruins encircled by rushing water, which Sonicalso needs to run along.

Shadow
In Shadow's story, he and Rouge go to Kingdom Valley because it is the extraction point for the Scepter of Darkness which Rouge obtained in White Acropolis. Shadow must use a glider to pass through some of the level and a Hovercraft to cover a large water body. Shadow is ambused by Dr. Eggman at the extraction point, which leads to Mephiles being released and taking Shadow's form. Mephiles then sent Shadow into the future into Crisis City.