Hypertuned/Resonant

[Rocl]

The battle at Yuzuka Manor is more important for this - he has Ame-no-Habakiri there as well, but never uses Art of the Sword...

Then you get to Ala Mhigo, and Zenos is using sword arts from enchanted katana and making illusory copies of himself.

Still catching up, but I want to point out this wrong--Ala Mhigo isn't the first time he uses these attacks against us. "The Time Between the Seconds" i.e. our match vs Zenos in Yanxia, he displays all of these characteristics. In fact the very first thing he does after unsheathing Ame-no-Habakiri is use "Art of the Sword!" His illusory copies are even called "Dark Reflections" and can be defeated in this solo instance.
Even in Rhalgr's Reach he's using Vein Splitter, calling down copies of swords (both the Storm and the Swell, actually) and what-not. Whether these are used via aether or not is, again, debatable, but honestly it feels that way. Gaius just kind of dropped some flaming ceruleum on the ground and used Terminus Est. Regula used Terminus Est and deployed turrets, iirc (his Ceruleum Servant is a whole 'nother can of worms, but I digress)

Vein Splitter, in particular, calls to mind of Nael van Darnus' initial use of Thermionic Beam in 1.1x; which was our original clue that she was no longer bound by the Garlean's genetic aetheric deficiencies. In this case he shoots a great blast from Bradamante which causes aether to erupt from the ground and severs an Aetherial vein. This is a very shoddy ground to argue that Zenos already has the Resonant procedure as of 4.0, but I suspect that Fordola probably wasn't Aulus' first run regardless. Given Zenos' big speech about wondering if Fordola was strong enough to survive the procedure I have no doubt he underwent Resonant procedure twice and that helps serve his proof as "I'm super tough guys."

Something that needs to be pointed out, I feel, is that Krile has something rather unique to her (in terms of NPC): she has the Blessing of Light. Whether Garlemald or Aulus knew this is debatable but it's a key difference between, like, her and Arenvald.

Personally, with very little evidence to help me, my headcanon is that the Resonant probably manifests as differently as the Echo (being that it's all but certainly an artificial version of it). We know that some Echo-users can't walk in the memories of others, and some can't listen to the whispers of a person's soul (omnilinguism)--that is, unless this has been retconned since 1.0 which is something I feel Moose might know better than I. It's possible that Zenos' Resonant didn't allow the 'anti-Echo' seeing of the future or something. I feel like we'll learn more as time goes on--I hope anyways. It's just as likely too, I feel, that Zenos' Resonant did allow him to predict his opponents attacks or something but maybe he decided against using it. ¯\_(ツ)_/¯