EchPiEl said:
My problem is that Descendant's effect uses the same template as Azathoth's, and by my knowledge, Aza's one does not trigger if it's not in play/blanked.
No, it's not the same template. Azathoth have 2 effects : The Response and a permanent effect. The last sentence is not part of the Response. You have a blank line between the 2 effects.