Greetings!
Sweeping Strikes (Ex): At 7th level, a Master of Chains gains the ability to make great, sweeping swings with his spiked chain. On each melee attack Master of Chains makes, he can choose squares he threatens that are adjacent to each other, and his attacks apply to creatures in those two squares equally. A Master of Chains can use this ability on any attack, even an attack of opportunity or a cleave attempt.
A Master of Chains cannot use this ability if he has moved more than 10 feet since the end of his last turn. If a Master of Chains drops one or both of his foes with a sweeping strike, he can attempt a cleave normally; however, he makes only one cleave attempt per sweeping strike, even if he drops more than one foe.
Constant vigilance: An opponent who enters into your threatened are must treat your threatened squares as difficult terrain, forcing him to move with caution.
Cheap shot: Any opponent that you threaten who takes any sort of movement provokes an attack of opportunity from you before they leave the threatened area. They are also unable to use the withdraw action to treat the square they start in as no longer threatened by you.
Special thanks to Dendu, for all the great suggestions/fixes/changes!