The king of Elfland's daughter influenced DnD, D&D

Gary Gygax lists it in Appendix N of the 1979 Advanced Dungeons & Dragons Dungeon Master's Guide, his published list of the fiction that shaped the game. Lord Dunsany is on it, and The King of Elfland's Daughter is the book of his that set the pattern for a perilous faerie realm lying just past the edge of the known fields, where time runs differently.