Saturn is using same Ability that Zunisha used on Momo
It's Level 02 Observation Haki, which allows you to "Share your Senses"
The Ability sounds useful to help Allies, but in Saturn's Case, He is a Demon who doesn't see the World like others do
Due to his High Haki Level, his "Insight" is way Superior than Most (It's like Bloodborne Game)
So when Saturn targets someone to let them see through his Eyes like Zunisha did, They are unable to grasp such Vision, their Insight is not good enough, it's like He is forcing you to see something that your Head isn't yet programmed to
Those who are too Weak, their Heads explode, while others who are fairly stronger, they still take Damage (Also same as Bloodborne's Frenzy Effect), He can do the same to Paralyze his Opponents (Not sure if it can work against Atlas though or Pacifista & Seraphim)
This Ability can be used by so many, Yasopp used it in Film Red, Kata can do it, Shanks & Mihawk & many others can, Marys from Onigashima follow the same concept, but it's supposed to be a Helpful Ability to be used with Allies, it's Saturn's Demonic Nature that makes this Ability Nightmarish & can be used against Enemies instead