Reality
Reality refers to "grounded" areas within cosmological space. This "grounding" serves to solidify and make sense of the otherwise chaotic nature of cosmological space and provides areas that beings can travel to, interact with, and inhabit.
Different realities are grounded to different degrees. A nearly-completely grounded reality will exhibit almost none of the unpredictability of cosmological space and will provide a space that beings can safely stay for extended periods of time. On the other hand, a reality that is relatively ungrounded may shift, or be strongly affected by emotion, or be seemingly random.
Deities and mortals have different levels of "grounding" required. Mortals require a more grounded reality, and most often have no control over any reality that they are in. Deities can influence realities - even completely grounded ones, to an extent - and are often most comfortable in slightly less grounded realities.
If a mortal stays within a reality that isn't almost completely grounded for extended periods of time, cosmological space can begin to have adverse effects on them, both physically as well as on their very being - past, present, and future. This can lead to memory loss, past events changing, and in extreme cases, untethering.