Sometimes, mice disappear. Many dangers threaten mice: so many predators try to eat them, and at their size, weather that larger animals shrug off can easily become life-threatening. Before they settled in mouseholds, wild mice died very young, and produced large litters simply in the hopes that some of their young would survive.
And yet, mice do not always die. Sometimes, a mouse presumed dead will walk up to the mousehold’s gates after months, or even years. What can mice really say about death, anyway? That practical streak once again inhibits them from saying more about death than they can really prove, so they refer to those mice they can see, and those mice they can’t see, whether missing, dead, or otherwise. Colloquially, they call these latter mice the Unseen.
Mice offer their respect to the Unseen, particularly those of their own family, belonging to their own frið. While easily mistaken for a spiritual practice, mice consider this simply practical. They cannot tell what influence the Unseen might have; whether they still live, whether in mouse form or some other. And even if not, the wyrd means that the actions of their ancestors still shape and influence a mouse’s present. Soliciting the favor of an unseen potential benefactor just seems like good sense.
At special ceremonies, a mouse might receive the honor of “being seen as” an Unseen ancestor, standing in for her and taking her place. During the Cataclysm, a practice arose out of necessity where a mouse might stand in for an entire lost family.