April 6th, 1862. The confederate army ambushed the union near the Tennessee River. The battle looked like it was going to be won by the Southern states until a union division of troops stationed farther north managed to come to the aid of their fellow soldiers. The battle left 16,000 soldiers wounded, and 3,000 soldiers dead, making it one of the bloodiest battles of the civil war. The medics were not equipped or braced for the scale of carnage that they had to face, a fact further emphasized by the reality that infection was prone to happen very often at this point in time. The soldiers had also spent two days fighting in the mud during rain, meaning that it was almost certain that any wounds that were received had been infected.
As the night fell that day, a strange occurrence started taking place. One by one, the soldiers that had resigned themselves to their wounds noticed that some of them were alit in a faint blue, casting a faint light on the now-dark battlefield. Disregarding that it must have made for quite a perfect nightlight, the fact of the matter is that the human body is not supposed to be glowing. As if a bullet wound wasn't terrifying enough, imagine being a soldier already half delirious from pain, and realizing that your intestines look like they're made of glowsticks. Stranger still was the perplexing realization that the soldiers that had this phenomena were more likely to survive. The soldiers then gave the glow the name of "Angel's Glow", with respect to the miracles it appeared to create.
However, the blessing was not given by the angels up above, but actually by the critters living in the dirt. The glowing was the doing of a bacteria called P. Luminescens and a parasitic species of worms called nematodes. The two species had a symbiotic relationship, where the bacteria lived inside the guts of the nematode, and the nematode hunted down insect larvae. Upon reaching the larvae, the nematode would puke up the bacteria, which were a bioluminescent species, emitting a soft blue light. The bacteria release chemicals that kill the other organisms trying to feed, and together the two are able to feed. However, they should not have been able to exist inside of a human body, since the environment should have killed them. They were able to survive due to hypothermia, a condition that many of the soldiers had gotten after fighting in cold mud and rain for two days. This resulted in a temperature that the species could survive in, and since neither of them was remarkably dangerous to the human body itself since the immune system could clear them both out, all they managed to do was kill other infectious species and then die, leading to the soldiers with the glow to be more likely to survive. Turns out that the soldiers shouldn't have been thanking the angels as much as the bloodthirst of some bacteria.