Short question: What happens if you view a Medusa while perceiving through another creature's senses, such as by Warlock's Voice of the Chain Master or Gaze of Two Minds eldritch invocations?
I'm asking specifically about Medusae, but this may or may not apply to other on-sight effects. The Medusa stat block states:
When a creature that can see the medusa's eyes starts its turn within 30 feet of the medusa, the medusa can force it to make a DC 14 Constitution saving throw if the medusa isn't incapacitated and can see the creature.
So, it seems there are a number of criteria that need to be met. Firstly, one must be within 30 ft. of the medusa. So if you are outside that range it's safe to say you won't need to make any sort of saves (your familiar is likely to be in a spot of trouble though). Alternatively, what if you are within 30 ft. while perceiving through you familiar? (Why you would be doing this is not important.) Does seeing through another creature's eyes count as 'seeing the medusa's eyes' as per the requirements? Would both you and your familiar need to make saving throws and potentially be petrified then?
Another potential scenario is this: What if you were completely controlling another creature such that they were completely unaware (i.e. not perceiving anything)? Would only you need to make a saving throw and have your own body be petrified while the one you were controlling remains unaffected? Or would the 'sight' of the medusa be transferred to the body that viewed it, rather than the mind?