In Siren's Port Simon will develop a dormant ability to produce and then breath into the atmosphere a slightly altered chemical from his universe known short hand as the Pax. A basic summary of what it does can be found
here. Simon's version differs in that once he stops producing the chemical it will dissipate any victims will come around after an hour or so, depending on how hardy they are and now long they were out.
The downside to this is that, like the original Pax, there is a chance (a 5-10% chance rather than the original .01%) it will backfire and instead of pacifying the victim, they become a
Reaver. (Warning! Possible triggers under that link. Reavers are scary, awful, and traumatizing by their very nature.) Luckily it would be temporary as well, though it will take a lot longer to wear off without intervention of some kind.
It will be a while before Simon even realizes he has this power and he will be using it very sparingly, but if anyone is interested in having their characters get Pax'd or even Reaver'd, leave a comment here and we can plot things out. Remember, Reavers are walking trigger factories, so please consider this carefully. I'm avoiding hard numbers about Reaverizing because I want whether or not it happens and how long it lasts to be up to the mun, but as it's meant to be a low chance of happening I'll have a limit. Nothing as crazy as five Reavers in a row, for example, and even two in a row will be very unlikely.
Any other questions about whether your character would be immune or not can be asked here as well.