§ Of Beren and Lúthien The Silmarillion

This doom she chose, forsaking the Blessed Realm, and putting aside all claim to kinship with those that dwell there; that thus whatever grief might lie in wait, the fates of Beren and Lúthien might be joined, and their paths lead together beyond the confines of the world. So it was that alone of the Eldalië she has died indeed, and left the world long ago. Yet in her choice the Two Kindreds have been joined; and she is the forerunner of many in whom the Eldar see yet, thought all the world is changed, the likeness of Lúthien the beloved, whom they have lost.