Riot Games posted an article on the new things coming with the PsyOps event and an explanation on how it loosely fits into League of Legends' lore.
PsyOps skin line is futuristic and that's pretty much all the info you need to figure out that it's not meant to be part of the main canon for League of Legends. With the disclaimer in place, let's get into the juicy bits of the story and the stuff we can look forward to.
According to Riot , Noxus has had it with the Black Rose Group in this particular timeline and the High Command formed up a spec ops team that could take them down along with the other enemies of the state. The requirement for the team was that the team members are "psychically gifted and physically unmatched".
The event has kicked off on live servers on September 3 and will last until September 30, 2020. In case you earn a pile of tokens but don't get to use them by the event's end, you will have time until October 20 to spend them. We assume Halloween event and a new skin line will make their way to League at that point.
If you're interested in the PsyOps pass, you are likely hunting for more Gemstones and Riot provided info on that as well. The event pass will have 20 milestones and the Gemstones will be earned at ranks 15 and 20.
Keep in mind that you will need to set aside 1,650 RP for the pass, which means you are likely to pay $15 / €15 but there will be some spare change after the purchase.