Previous spells were found in a place called "RuneforgeLegendaryAbility", and since so many of them are old set bonuses and Legion Legendary effects, it's likely that those are related to the upcoming Shadowlands Legendary system. However, the spells in this post were not found in the same location but were uncategorized. Most of these are still related to old set bonuses and Legion Legendaries, so it's possible that these are in-development Legendaries or something completely unrelated like Anima Powers.