The witches were once hidden protectors, guiding humanity through their darkness, hidden in the shadows. But humanity, not understanding their purpose, discovered, persecuted, and executed them. Those who remain wish only to destroy humanity. Only one witch, Gretchen, yet wishes to help humanity. The only way left is to stop the other witches by whatever means necessary.
Another, a man named Heinrich, was once an executioner, performing his grim task in the darkest days of the witch hunts. As such, he wound up cursed with immortality. To atone for his deeds, he enters into a blood contract, the Knight's Contract, with Gretchen, sworn to protect her. In return, he will be released from his suffering once their task is complete.
Knights Contract is a 3D hack 'n' slash with a twist: the player's character, Heinrich, cannot die -- if he takes too much damage, he will literally fall apart and have to pull himself back together -- but his partner, the witch Gretchen, is still mortal and must be protected. Heinrich himself wields a large scythe with a wide variety of deadly moves, and he can also call on Gretchen to assist with several different magic spells. Heinrich can acquire additional equipment during the game, while Gretchen's magic can be upgraded using souls acquired by defeating enemies.