Merfolk live in pods of four to five fated mates, all capable of producing eggs and sperm, but reproduction is decided through a ritualized fight during fertile cycles: the loser gets pregnant. Once submission is clear, the winners—who have fertilized internal eggs—implant them all into the loser’s single shared gestational chamber, where the eggs intermingle rather than being separated; the gestator contributes no eggs that cycle, only body, nutrients, oxygen, and risk. Their anatomy is evolved for this role, with an elastic, highly vascular brood cavity and a temporarily suppressed immune response, allowing them to survive carrying multiple unrelated embryos. The eggs develop slowly at first, then hatch internally and continue as live young, culminating in a live birth in a guarded reef or cave. Parenthood is attributed to the egg-contributors, while the gestator is honored for enduring the cost rather than considered a genetic parent. The system persists because pregnancy is burdensome, fighting favors stronger members remaining mobile defenders, everyone eventually loses across a lifetime, and harming or killing a gestator is one of the gravest taboos, since the pod’s future literally depends on protecting the one who lost. This all falls apart when a human woman becomes their mate. Fate is cruel. Now the pod must figure out of to make this work when their mate is a human female.