[Disclaimer: If you're part of my ECLIPSE campaign, please don't read this thread!]

So, I've recently decided to run a second campaign. The premise of the campaign is that strange magical surges of time-based magic are causing varying-sized areas to disappear, while simultaneously those areas are replaced with the same area, just from the distant past. The present time in the game is very modern (think our own times).

I've already got the idea that people may be appearing in these, and need "Rehabilitation" as the company that oversees these phenomena are calling it. I'm here asking for other creative ideas for strange shenanigans that could happen as a result of these time rifts!

Thank you in advance! (:

Well, there will be people and creatures who accidentally wander in and out of those areas and end up stuck out of time. And since time is jumbled, someone could meet a duplicate of themselves who just got back from the past when the original hadn’t even gone back yet. Stuff like that.

I suggest you check out Infernal Machine Rebuild. It's got a lot of time shenanigans.

It sounds like what you're planning has commonalities with the episode Time and Again (Star Trek Voyager).

Specifically for shenanigans:

You might end up with a Thanos situation where an arch-villain that is dead in the modern timeline attempts to exploit the rifts in the past. Learning of their impending mistakes, they either win their fatal conflict and change the current timeline, or pass through the rift and start a fresh reign of terror.

Or, time manipulation is extremely unstable, and the rifts catch the attention of extra-dimensional time cops, a la Umbrella Academy.

Or, there could be some environmental changes that have occured, and that is the threat to be worried about. Many of the biggest threats of time travel aren't dinosaurs or cultural differences, but rather diseases being transmitted back and forth. Maybe the nature of magic itself naturally changes over time, and by bringing a slice of the past/present into an alternate time you get arcane storms as the different magic potentials collide and mix like hot and cold air.

There are plenty of time-travel specific shenanigans like grandfather paradoxes, multiverse duplications (Council of Ricks), or multi-dimensional interventions, but traveling through time is basically just traveling through space with different steps. Any dangers you associate with traveling to a different continent/world can similarly apply to traveling through time. Heck, with continental drift and climate change, an entire city could end up trapped inside of a glacier, or at the bottom of the ocean.

Have it so if a player dies, any of their decendants back-to-the-future fade, but only proportionally to relationship. So if a guard kills a PC, then a finger or two might fade from the guard, and you can wink and nudge.

Change all future NPC statblocks to know "LOLcommon" instead of common. Language would have changed enough that the players can basically only communicate with other warped people or linguistics experts. (I assume the players came in from the past)

Enterprising buisnesspeople immediately try to cash in, such as trying to get back in time, deposit 10,000 dollars, and collect it in the modern day WITH INTEREST. OR go full back to the future 2 and bet on all the right wars and mines to get real rich.

BEST IDEA HERE: in the history books, the times that the places swap with are marked by chaos and a sudden, unexplained shift in culture and technology and only now are people realizing why

PS permission to steal plaigarize use this concept at some point?