phantom touch gets applied after the attack.

the tl;dr as to how to approach block revive champs (Fenax and Inithwe come to mind) and anything that is bonus damage (phantom, reap, wm/gs)

those bonuses are perceived as not coming from the champion themselves as a source of damage and thus will not let you block revive

But does the phantom touch damage proc before or after? What if Fenax gets his second attack, would it go A1 first attack, phantom touch, A1 second hit?

I've been seeing a lot of fights where I was absolutely sure (and ill concede it's possible I was wrong) that Fenax would make the kill with just his regular A1 but then block revive didnt proc.

For instance, an unkillable wears off on Leo, hes at 1 hp, Fenax attacks with A1, Leo goes down but DOESN'T get block revive

I'll see if I can get an official answer but my gut feeling is the damage is the damage is applied simultaneously, and just shown separately visually.

my fenax also has phantom touch and i use him in the arena quite a lot, iv not really noticed it stopping him from landing his block revive, from what im seeing im landing it on 90% success rate, iv never really noticed if deathtouch is stopping it from working at times but iv also not really been looking out for it.