This small, delicately-painted terracotta vessel has a variety of uses — mostly mundane. The knowledgeable owner, however, will be able to use it in this way:
Fill the vessel with wine and just the right mixture of herbs, then allow it to steep for at least one hour. (There is no maximum time; if you cover up the openings so it doesn’t spill, you could carry around a properly steeped mixture indefinitely.) When you pour the wine back out, it will quickly congeal and solidify itself into the shape of a mouse. This can be done only once per week.
The resulting mouse is somewhat smarter (Int 5) and more attentive than its mundane kin, but is not compelled to do what you want. If you give it a small treat or a skritch behind the ears, though, it will stick around long enough for you to make a Handle Animal (or equivalent) check.
Casting speak with animals or using an equivalent ability gives you a +5 on your check.
If your initial check is high enough that the mouse remains with you for another day, you get a +1 bonus on your Handle Animal check towards the mouse the next day. These bonuses stack — if you’ve kept the mouse around for two days, you get a +2, &c. However, the bonus only accumulates as long as you are kind to the mouse. If the mouse is unhappy with your behavior on a given day, you get a -1 for that day instead. If your bonus on this check ever becomes so high that it is impossible for you to roll below 25, then the mouse is your pet permanently and you no longer need to roll, unless some egregious mistreatment drives it away.
Note that the mouse, while smarter than most mice, is not as smart as a human. At the GM’s discretion, the mouse will need to make an Int check to perform more complicated tasks.
You may use the normal Handle Animal rules to train the mouse if it sticks with you; its ability to learn scales up with its Intelligence as consistent with the system you are using.
N.B. If the player manages to accumulate several helpful mice, the GM may, at their discretion, start requiring the player to spend a certain amount of time each day playing with the mice to keep them happy & on side.
N.B. If the player is mean to the helpful mice, the GM should remember that these mice are smart enough to understand the concept of "sabotage".
Citation: This was inspired by this museum piece.