Ranni, except small enough to fit in your hands. Note that Ranni is already petite.
Once the Tarnished progresses far enough in her quest line, Ranni will tell them that she needs to hide for a while and vanishes from her usual location. A small doll that looks like her can be found later. Speaking to the doll will reveal that Ranni has shrunk herself.
This tag implicates ranni_the_witch (learn more).