Bucket of Rats

Wonderous Item, Uncommon
A old, dented steel bucket with a small wooden grip on the handle which appears to have been chewed on by a small animal. When unattended it will occasionally rattle or jostle with no apparent cause.
As an action you can slam the bucket into the ground or against another flat surface, causing 1d4 rats (using the statistics from the Monster Manual) to crawl out of the bucket. These rats immediately attack the nearest creature other than you. As long as the bucket remains where you placed it, at the start of your turn an additional 1d4 rats crawl out of the bucket and attack. If 12 or more rats from the bucket are present at any one time, they become a Swarm of Rats (again, see Monster Manual) and the bucket falls over and summons no further rats. Once the bucket has been used, it cannot be used again until 7 days have passed.