A slightly more NSFW version can be found here

The Custodian examined the implants in his chest with a delicacy befitting such divine artifacts. To have one's flesh graced by the figurative Right Hand of the Emperor would, under any other circumstances, have been considered a profound honour for a Space Marine. Titus shuddered.

"My poor gene-seeds," the Custodes pouted. "Look at these paltry things. They’re half the size they were when first implanted in you."

And yet they felt twice as heavy, Titus thought. His frail frame trembled beneath the weight of his ceramite armor. His body had rejected the gift, and now the two sets of gene-seeds were at war within him. Her Glandulae Lactiferae had all but beaten his original implants into remission.

"Then remove them and be done with it," he snapped. "There are a million worlds that need me."

"And waste five millennia of research? Heresy," she tutted. "No. I am confident the gene-seeds will find equilibrium. At that point, you may be harvested, and the refined seeds will birth the first generation of female Astartes. It will simply take time to find the balance. Barely a moment."

Titus relaxed. Briefly. Until...

"How long is a moment to a Custodes?"

"Oh. Nothing more than a century or two," she replied airily.