"Seul" is "alone" in spanish, but its used as a pun on "soul" as well; "kè" is heart in creole. This was previously named Ezili, when it was a full island. Now, it is shaped vaguely like a human heart, sometimes drowned in water.
It's clear that Erzulie used to lay here by the shadow in the water left behind, as well as the land being left behind. Ironically, while Erzu created the rule that swords to the heart kills gods, it is a custom to leave the sword of the deceased struck into the heart-shaped island.
Sol stays here during and after the Darkness era.