I wrote a triggered action ("Defy Reality"), but it looks like I accidentally cut it in layout... I really don't know how to feel about the fact that it took until now for someone to say something!
Regarding the stability potency: I looked at the data the lovely folks in the brewey complied on all the core monsters, and comparing [highest characteristic] to stability works on approximately as many monsters as a strong potency vs. Intuition or Reason would, at all four echelons. (Not the same monsters, obviously, that's the whole point, but about as many.) Given that, the question is whether a strong-potency EoT slow is stronger or weaker than 3 extra damage on collisions (at echelon 1).
Back With a Vengeance does do a lot, and that was purposeful; I expect it to be hard to use, partly because you're already 6th level when you gain access to it. You get what amounts to a teleport 5, a chance to spend up to four recoveries (five if you want to be wasteful), a full condition cleanse, and a free strike. In exchange, you have to horde 9 ferocity (instead of spending it early on killing the enemy), then spend it on this (instead of on killing the enemy). I mainly like this ability for how it encourages otherwise-suicidal play, leaning into the fury's "hit me!" mentality.
Sorry to hear it felt more Null than Fury to you; I did put effort into making the Eternal its own thing and leaning away from the Chronokinetic's flavor. Rather than "I have meditated my way into total harmony with the temporal dimension," I was going for "I am a warrior of the outer chaos, your flimsy reality cannot constrain me." Are there any changes that might help that land for you? On reflection, I might have had room for a flavor introduction at the top... (only because I accidentally cut the trigger, though)
Thank you for the detailed feedback!