When the next expansion to Rift goes live, players will have the ability to access a new level of skill called Legendary Powers. Legendary Powers improve on already existing skills by adding new mechanics, effects or by making them more powerful. Legendary powers are obtained between levels 66 and 70 with players able to add up to 3 abilities for each Soul.
Not every ability in every Soul is able to become Legendary, but there are a variety available at different points in each Soul’s tree. These powers are specific to a particular role, so you can have entirely different Legendary powers in every role slot.
The blog post provides several examples of the type of abilities that players will gain access to in Starfall Prophecy.
You can read more on the Rift site.
In addition to the above there is also a blog post that provides lore details for the Temple of Ananke. Check it out here.