Finders. Firstborn, Lastborn, #1

Cassilde Sam is a barely solvent salvage operator, hunting for relics in the ruins left by the mysterious Ancestors-particularly the color-coded Elements that power most of humanity's current technology, including the ability to navigate through hyperspace. Cassilde is also steadily fading under the onslaught of Lightman's, an incurable, inevitably fatal disease. She needs one last find big enough to leave a legacy for her partner and fellow salvor Dai Winter.
When their lover and former colleague Summerlad Ashe reappears, offering them a chance to salvage part of an orbiting palace that he claims contains potentially immense riches, Cassilde is desperate enough to take the gamble, even though Ashe had left them both to fight on the opposite side of the interplanetary war that only ended seven years ago. The find is everything Ashe promised. But when pirates attack the claim, Cassilde receives the rarest of the Ancestors' Gifts: a change to her biochemistry that confers near-instant healing and seems to promise immortality.
But the change also drags her into an underworld where Gifts are traded in blood, and powerful Gifts bring equally powerful enemies. Hunted for her Gift and determined to find Gifts for her lovers, Cassilde discovers that an old enemy is searching for the greatest of the Ancestral artifacts: the power that the Ancestors created and were able to barely contain after it almost destroyed them, plunging humanity into the first Long Dark.
Haunted by dream-visions of this power whispering its own version of what happened, Cassilde must find it first, before her enemy frees it to destroy her own civilization.