“You said that . . . there are two types of venom?” Tine asked without slackening her efforts to maintain Gilgamesh’s Spirit Origin. She seemed to be grasping Enkidu’s personality, because the side of her that had been built up as a mage began to show on her face.
“Yes. The other is closer to a curse than a toxin.”
Enkidu narrowed his eyes as he surveyed the wound gouged in Gilgamesh’s torso.
“. . . I suppose this is what they call ‘irony.’”
“?”
“I don’t suppose it was a rainbow-colored light that impaled King Gilgamesh’s body?”
“. . .! Do you know what that was?”
The scene of Gilgamesh being struck down replayed in Tine’s mind.
The seven-colored halo, distinct from the titanic mechanical “something.”
The way it had twisted into a shape like the tip of a rock drill and impaled Gilgamesh through the belly.
“That was the protection of the gods. It’s also a curse to the human race. . . . The light that was poured into Gil was one of them, a curse descended from Pestilence.”
“Pestilence . . .?”
“We should probably be grateful for the hydra venom. It and the pestilence are competing with and consuming each other. . . . That’s why the plague hasn’t spread from Gil’s body. If not for that, there’s a high probability that all of you, and probably me, would also be trapped in the abyss of death by now.”

Fate/Strange Fake: Volume 6, Chapter 18 ("As Dream and Reality are Both Illusion I")