Ascension is a part of the Cycle Aspect of the Marrow Fysa.
This is a passive fysa. An individual who has access to a vast amount of magic or experience might be able to tap into a new more monstrous form temporarily. Some have been known to lose themselves in this state however if triggered prematurely. These greater forms can also be accessed with practice and used with less worry when they've been "earned" rather than assumed through sheer force.
Ascended forms break the boundaries of conventional species anatomy, and can grant any number of physical boons or mutations as reflects the soul of the user: Ascended forms can be roughly 50% larger than normal beast form. The base would be similar to the beast form, but there's no limits to physical traits-- multiple limbs, multiple heads, multiple wings, gills, fins, transluscent skin, the sky is the limit.
If you are not a leyr, this ability also costs a balanced feather in addition to other learning costs.