Just came on this product and thought it may be a viable alternative for world building, since it has been announced that Realm Works is sunsetting.
https://www.patreon.com/legendkeeper/overview
Thus far it is inexpensive, and for a beta, I have not found anything that does not function. I'm hoping enough interest will keep this project around. It is not as feature rich as Realm Works or World Anvil, but is elegant and has enough in it to suit my needs.
It is difficult to put into words my feelings concerning Realm Works demise and the years of waiting for Lone Wolf to move toward its customers. Understanding development is a complex process, I have never seen a company that would not grow to meet demand, and it seems a strange business model that would not be set up for lasting success. That being said, I loved Realm Works in concept and general functionality and am saddened to move away from it.
Hero Lab and it's online iteration seems to be moving in that same direction, and since there are fewer years ahead for me than behind, I have to give serious thought to another decade invested. Nevertheless, I wish the company and its owners all the best.