The power of numbers: you have gained the magic system the humans use in DxD. Through the power of research and calculation, you are able to emulate the power of devils. Though the devils can bring about their vision of reality through pure imagination and will, yours is different in that it takes study and equations. Through this magic, you can wield various powers such as illusion, hypnosis, healing, enchanting, and other effects. Teleportation's would require calculating the distance and the energy required, while casting a fireball would require the calculations required for the fireball and the forces that would affect it.
With enough study and preparation, you can affect more of the world around you, producing effects that the humans of the DxD universe could only dream of.