Thetis is a sea goddess. The other gods forced her to marry human king Peleus despite her disgust for humanity and sex. When her and Peleus’s son Achilles was born mortal, she was preemptively heartbroken at the thought of her son’s death, which rendered her a morbid, anxious, and emotionally unreliable mother. When Achilles was about seven, she abandoned her son to return to the sea, devastating him. She periodically visits Achilles from the sea throughout the novel. After Achilles’s beloved friend Patroclus is killed in battle while wearing Achilles’s armor, Thetis visits Achilles in his grief and offers to give him divine armor to replace the set that the Trojans stripped from Patroclus’s body—though she also reminds Achilles of the prophecy that he will die if he continues fighting in the Trojan War and kills the great Trojan warrior Hector.