So I figured I’d use the Astrologer to get the chance to cast Parasites before Friden’s creatures go to town on my team However, he then killed my Sandstone Imler without any ill effect…
Update: after it was pointed out that Friden would need to be <100% Health for healing to happen, I tried again, this time with Everything’s Gone. Eventually, the enemy’s Ruby Carbuncle attacked my Diamond Imling, but still no healing:
Even though Ruby Carbuncle was clearly below 100% Health:

Maybe Leeching just didn’t trigger because the damage was redirected with Patriarchy?
Update 2: Now I tried using Sorcery Transformation along with Everything’s Gone, and cast a bunch of Mutilates and Bangin’ Bourbon at Friden and his cohorts. I am pretty sure that this should have worked. Still, not a scratch…
Windows 10