The raze could be something along the lines of a raven's feathers bursting out from the wind and the ult could be a trail of crows soaring out to replace the souls. If need be the portrait for the passive could be Eye of the Raven or something along those lines.

I want a custom Requiem effect, maybe replace the wings on his back with crow ones. But who knows if it will happen :(

I not quite sure if the patch will make it any easier.

Requiem of Souls damage lines travel distance rescaled from 975/1000/1025 to 1000
Requiem of Souls Starting Width increased from 75/100/125 to 125
Requiem of Souls End Width rescaled from 400/425/450 to 425
Scepter now also increases Necromastery max souls from 15/22/29/36 to 22/30/38/46