Sosidge appears as a perfectly normal ferret, but has uncanny intelligence, which paired with the standard amount of ferret mischief, results in extraordinary shenanigans. Sosidge resides in a little wooden box, which aside of some simple carvings, is plain and a bit worn. Using the box to store small items is possible but not recommended, as they may disappear. Sometimes small items may randomly appear.

Whenever Sosidge gets tired, wounded, or bored, it goes into the box and disappears. If Sosidge likes you (and feels like it), it will come out of the box when called and the lid is lifted, and may even attempt to assist you. The longer you know Sosidge, the more it will understand your communication and even comprehend your situation on its own. If Sosidge dislikes you (or you picked an inconvenient time), it will make its business to annoy you, and may bite you if you attempt to call it. Sosidge enjoys treats and is susceptible to bribery.

Sosidge has the physical attributes of a normal ferret. If Sosidge dies, its body disappears after three hours. The box will lose its special qualities for an indeterminate time. After three days at the earliest, Sosidge may emerge from the box again, prompted or on its own. It retains its form and remembers whatever it experienced earlier, but will act more like an ordinary ferret for some time, gradually regaining its smarts and higher motivations.