Would guardian set activate Mortu Macaab's passive?
I have a Mortu so ran a few tests, and can confidently say that taking damage through the guardian set does not proc the Firey Rage passive. Other champions in my team took more than 50 hits during my test, all of which triggered the ally protection for Mortu and the guardian set, but none of which triggered the passive opening up Peril.
At 20% chance, even with the worst luck I would have expected at least a couple during those 50 hits. My conclusion is that the attack needs to be targeting Mortu for the passive to have a chance of triggering