The nature of portals ensures that GM’s have total control over how incursions manifest, and thus over the exact nature of adventures in the setting. From small mysteries that only obliquely involve other Realities, to a massive, full-scale invasion from another world that’s spread across several states, converting entire regions to the intruding Reality, the nuts-and-bolts of portals allow the GM to run the game he wishes.
Each incursion is different. A portal may allow beings from another world to cross over. It may allow PC’s to enter the alien world. (And adventure there as long as they wish.) Since portals open and close all the time, the effects need only last as long as the GM desires.
Portals can be customized in other ways. The six Threat levels (see Post II) allow for a great variety of possible incursions.
At the lowest level, weird things just happen. An adventure that deals with low-level spontaneous phenomena that emanate from another Reality is possible, such as an entire town suddenly being affected by post-cognition. (Touch your spouse, and you experience what they’ve done in the past. Chaos ensues.)
Or, an artifact left over from a previous incursion suddenly goes active (a Threat-2 situation). There are myths of ancient beings who visited an area? They left behind a mysterious sculpture, carved from an unknown substance, that is supposed to be a mechanism but it does nothing. A second incursion, and it goes active, causing any one of a number of effects. Perhaps spontaneously uplifting animal species, making pets sentient. (Not to mention what happens at the local zoo.)
These kinds of incursions require far less work than a Threat-4 or higher. As the alien Reality isn’t directly involved, the GM only need devise the specific phenomena or artifact, not an entire Reality. Higher Threat incursions require more work, but are usually more spectacular.
Threat-3 situations occur when people in our world begin acting like people from another world. Imagine an entire city suddenly granted super-powers and the 4-color morality of the Comics Code. Monologuing villains, stalwart heroes, and helpless innocents. Bright costumes, dastardly plots, and battles that level whole buildings. Now, instead of “superhero comics”, substitute “fantasy world” or “cyberpunk dystopia” or even “cyber-fantasy dystopia”. (Or, really, any setting/genre the GM wishes.)
Portals allow for all of that.
[Continued in Part V.]