The Talisman of the Raven being used
Shapeshifting, or metamorphosis, wasn't just about your species' biology; it was also about using the Force. With old magic or objects powered by the Force, someone could transform into another person, creature, or thing by channeling the Force.
While the masquerade trick was around, changing shape wasn't super common for Force users like the Jedi and Sith. However, the Nightsisters of Dathomir, mysterious witches, were all over it. They used Talismans of Transformation and Dathomiri illusions to morph themselves.
On Dathomir, the planet, Nightsister shamans made these special Talismans of Transformation. They were like rings or necklaces that had Allyan Magic woven into them, letting whoever wore them change shape. Each talisman only let you become one specific creature by connecting to its "ur-spirit"—basically, the main spirit for each species in the spirit world. The Jedi scholars and Sith couldn't figure out how these things worked. Also, the Nightsisters sometimes rode black stallions that could also shapeshift.
Charal, who called herself the Witch-Queen of Endor, had one of these enchanted rings. It was lost on Dathomir when Talzin was in charge, and it allowed her to turn into a raven. Charal used it a lot, like during the Ewok–Sanyassan conflict in 3 ABY. Once, she turned into a beautiful princess-like girl to trick Cindel Towani. But, it's not totally clear if she used the ring then, or if she used an illusion, a Force-powered cloak, or some other method.
The Ones, a super strong and immortal family from Mortis, could look like anyone or anything they wanted. The Son often turned into a winged gargoyle, but he also used the face of Shmi Skywalker Lars, who had passed away, to mess with her son, the Jedi Knight Anakin Skywalker. The Daughter, another One, would take the form of a big, glowing griffin. Similarly, Abeloth, a Force being, could steal the looks of people she had eaten.
Ros Lai, a Sister and the daughter of Clan Mother Zalem, was known for using the art of illusion to appear as a gross hag called "the Rancor". She started turning into the Rancor when she was young to hide her plans to get revenge for her dead father. When she was alone, she'd go back to her real form. Around 31 BBY, Jedi Knight Quinlan Vos came to Dathomir on a mission from the Jedi Council to stop Zalem from using a Star Temple's Infinity Wave against Coruscant, and he saw Ros Lai shapeshift with his own eyes.
Another Nightsister stuck on Shira could shapeshift into anything that was between 1.5 and 1.9 meters tall and weighed between 40 and 80 kilograms. She could stay like that for hours.