Looking around the room, the situation was becoming ever more heated. With astartes of varying kinds becoming increasingly hostile to each other, risking to have at each other at any moment.
Zuriel needed to make something, he was tired of this useless rivalry. It was time to exert his power over the situation.

After having cast himself into the depths of loss and despair as he crept along the corners of the room he realized his folly and began to exert his will over those around him. Knowledge is power, and he held that knowledge. For it was given to him by the liber mechanicum.

All around him was medical machinery, some of excellent quality and of ancient design. The best available for mortal standards.
He knew there was better, especially for his ends. Alas he could not be picky and went to work.

He made sure he was out of immediate sight, or at least wouldn't be shot instantly when the marines started firing.
Behind him the situation was becoming more and more heated as the renegades were performing surgery upon the techmarine.

Opening the liber mechanicum Zuriel flipped quickly through the pages until the correct page was showing. He had no idea which page was the correct one, nor was there any way to know if it was the correct page since the pages lacked numbers, letters or illustrations to differentiate them from each other.
But this was the correct page, he was sure of it. He ripped a small elongated piece of the parchment from the top right corner and put it down in front of him. Took a vial and using a tweezer he put the piece inside.
With a moment of hesitation, Zuriel froze, flipped a dozen or so pages, ripped another piece out and put into another vial.

He filled the vial halfway with water, took some of the oil which dripped from his robes and put into the vials. Gave a quick whirl and then ran his fingers across a multitude of samples. Stopped at one and snagged it from the storage.
Emptied the vial roughly equally in the two experiments and finally corked them and watched them as they blended.

Black swirls were going inside the vials, dancing, defying gravity.
Excellent, even as he can't focus energy inside here. It seems the already defiled materials still held much of their potency.
After a while, after hearing the chain blade of a narthesium go into full whirr Zuriel took samples from the two vials. And checked them in a microscope.
The virus samples were alive, and they were hungry. They were happily attacking the skin cells of the parchment from the book. Since it wasn't parchment at all. It was leather. Probably human by the look of it.
Perfect, the samples were having the desired effect. The virus was mutating. He marked the two vials, the first red, the second green before putting them in a pouch on his person.
He also made sure to snag a hefty syringe, he would need it for later.