The Kingdom of Mercia (also referred to as the Kingdom of Snottingham) is one of the Mobian kingdoms on Mobius, located across the sea and some distance away from the Kingdom of Acorn. The Kingdom fell into severe decline after the despot Dr. Ivo Robotnik managed to take over the Kingdom of Acorn and spread his empire throughout Mobius. The Kingdom of Mercia was eventually overrun by Robotnik's forces, and Robotnik's sub-boss known as the High Sheriff was installed to ensure any rebellions were quelled. Those who managed to escape capture and roboticization at the hands of the High Sheriff and his Robian followers moved to Deerwood Forest, where Rob O' the Hedge became king. Rob also led a group of Freedom Fighters known as the Crazy Kritter Freedom Fighters in an attempt to end the High Sheriff's rule. The group's efforts failed, and all of the members of the Crazy Kritters except Rob were captured and roboticized.
After Robotnik died and the High Sheriff was apprehended, the Kingdom seemed to regain some of its territory and freedoms, despite the coming of Dr. Eggman. Contact continued between the Kingdom of Mercia and the Republic of Acorn, and Rob remained the region's king.
Deerwood Forest is a forest area located by the Kingdom of Mercia's territory (similar to the Great Forest and its location to Mobotropolis). After Dr. Ivo Robotnik expanded his global empire and took over the Kingdom of Mercia, he placed his sub-boss, the High Sheriff, in charge of Mercia to round up and roboticize locals and supress any resistance groups. Those who managed to escape captured and fled to Deerwood forest. Rob O' the Hedge became the king of Deerwood during the time the High Sheriff controlled Mercia. He established the Crazy Kritter Freedom Fighters to oppose the High Sheriff, and the group operated from within Deerwood until all of its members except Rob were captured and roboticized. The Lost Tribe wandered through Deerwood forest during their quest to locate Albion. Since the High Sheriff was sent to Knothole and had his free will restored, the Kingdom of Mercia was reformed into the Kingdom of Snottingham where Rob is presumably still king. Deerwood is likely a part of the new kingdom's territories.
Rob O' The Hedge
Lord Mordred Hood
The Mercian Freedom Fighters
The Mercian Dark Egg Legion