Manipulation is the ability to alter existing spells. It is in many ways the opposite of Enchantment.
Manipulation at lower levels allows the user to tweak or alter an existing spell, or to remove a small enchantment. At higher levels, manipulation can completely re-write an existing enchantment, or unmake a large spell. Unlike Enchantment, manipulation may be done on the spot.
Manipulation is complimentary to Shielding, but can also be used creatively to fuel other types of magic.