Board Thread:Questions and Answers/@comment-83.204.115.97-20170416220442/@comment-85.229.234.232-20170418101342

Well seeing as both players and NPC's are created into the new world in their game avatars, it should be safe to assume that both NPC's and players both have the same physiology if they are the same race. So a human NPC and a human player should both be fertile unless they have some special backstory, skill, curse or whatnot that prevents conceiving children. I mean there are children of players, so it should be safe to assume that NPC's can also have them.

However, an NPC will most likely never have a child unless a player directly tells them to make some, also while some race combinations are impossible, in the story there have been some mixed races shown like a half-elf or the human queen with dragon blood. Overall as mentioned above most likely humanoid races can interbreed but they can't breed with demihumans perhaps. A lot of the lore is based on H.P Lovecraft and a lot of western and eastern stuff.

In a lot of those kinds of stories/legends, it is fairly common for demonkind/heteromorphs to impregnate female humans to give birth to demons/monsters or half-demons.