Apparently the yokai Saturn's Zoan form is based off, the Ushi-Oni, has the ability to drain the life of anyone that sees it, so it seems like a thematic version of that. I assume generally anyone below that Marine rank doesn't have the haki to resist the ability.

I feel like for Kizaru's character it doesn't matter if he's serving a literal devil since he's a self impose slave to authority.

But yeah powerscalers BTFO lol