Immanence is when the otherworld draws close to the mundane world. It’s triggered in times of crisis. GMs, you can trigger an episode of immanence whenever an aspect related to the spirit world or a spirit is compelled; often, an inconvenient episode of immanence is a suitable event compel in and of itself.
The flavor of the triggered immanent episode should be relevant to the compelled aspect, whether a spirit’s portfolio aspect or an issue aspect. Immanent episodes can also be triggered by compelling a character’s appropriate aspect. In this case, the episode—or, at least, its initial circumstances—should reflect the character’s initial encounter with the otherworld.
A character’s experience during an immanent episode depends on their level of connection to the otherworld. Characters with a strong connection—including all mediums and any other character, PC or NPC, with an aspect representing their relationship to the otherworld or to a spirit—have a clear experience and memory. As the otherworld draws near, they can easily pick out its details, tell them apart from mundane reality, and have full memory of events.
Important characters without a connection—generally, main NPCs and non-medium PCs—have a clear experience during the episode. They can perceive details of the otherworld, and react to and interact with them. However, it is difficult for them to tell what is real and what is otherworldly. Doing so requires a Will roll, with failure resulting in some catastrophic misinterpretation. After the otherworld recedes, these characters’ memories become vague and fuzzy. They might question their own experiences or pass them off as a daydream or fanciful delusion.
Supporting NPCs have a muddled, confusing experience from the start. They might see features of the otherworld out of the corner of their eye, or see things blur back and forth between one state and another. Their experience feels like a waking dream. Characters who are easily upset or don’t handle the unexpected well might freak out, but even people who keep their head cannot interact effectively with the otherworld. Their impaired perceptions mean these characters are extremely vulnerable during an immanent episode, and can be injured, mentally scarred, or even killed or driven mad by spirits. Without a medium around to help resolve matters, immanence rarely ends well for these characters. The memory of the experience typically fades quickly, as dreams do, but some details might remain.
Nameless NPCs are even worse off. They’re unable to perceive the otherworld at all, and if an otherworldly element that manifests during an immanent episode winds up interacting with them, they’re likely to react with surprise and confusion. Like supporting NPCs, they’re extremely vulnerable when the otherworld becomes immanent, and they never remember any details of the experience.