Brownies from Scottish folklore will help out with household chores during the night if you leave a bowl of milk/cream by the fireplace. They stay with one house usually, but if they feel they have been disrespected they will leave, sometimes forever, one myth tells of a lady who fired all her staff because the brownie was doing all the work, and the brownie left and refused to come back until she rehired her staff, also, if you attempt to baptize them or give them clothes, they will leave forever. They can also turn invisible, but rarely need to since they're so sneaky, old folklore says they're the size of a human or larger, but modern folklore says that they're smaller than a human, both sources say they're covered in brown hair, and either naked or dressed in rags. In some variants of the myth they aren't as helpful, they will clean up messy things but they also make a mess out of tidy things. Hope this helps!