In which book did alien protagonists absorb and mutate humans, turning their flesh into biological weapons that they then used against other humans?

Question

In which book did alien protagonists absorb and mutate humans, turning their flesh into biological weapons that they then used against other humans?

I believe the book starts with a human encountering a lone member of the alien species, who promptly subsumes him and uses his flesh to make weapons that it can use. It then goes in search of more raw material..

I think the human discovered one of the aliens when he was atempting to salvage a small object adrift in space. If I recall correctly, the human then crashed his ship on earth. I think the aliens were more insectile (lots of legs) and could control a human by inserting a proboscis into their spine.

Once they didn't need the intact human, they injected them with something (nanotech?) that let them repurpose the flesh and bones into new forms. This could be done to dead humans too, as long as the body hadn't significantly decayed.

The aliens had previously lost an interstellar war and were believed to be extinct. The species had different casts, with the one at the start of the story being an infiltrator/scout.

I probably read the book between 1983 and 1999.

Answer 1

Per the OP's comment:

I think I've found it, "The Vang: The Military Form" by Christopher Rowley.

This is The Military Form (1988) by Christopher Rowley and the second book in The Vang trilogy.

Eons ago, a war was fought to the death between the parasitic and ferocious Vang and a gifted but doomed race. As a last resort, these gentle beings were forced to use the Starhammer to smash the Vang spacefleets and homeworld, leaving only a handful of survivors. For a billion years a silvery shape drifted through space. More than three thousand years after humanity first went to the stars, an asteroid miner named Seed of Hope was illegally prospecting for radioactives in the Forbidden Areas of the saskatch star system. There it chanced across an alluring silvery object which looked like it would fetch a good price in the market for alien antiques. It was an encounter most of the crew would never remember.