Aisling

Aisling is a demi-god, the princess of the now destroyed Tuatha Dé Danann, living in the woods outside of Kells. She is a protector of the forest, and doesn't like unwelcome guests. At this point her age is uncertain, but she is likely to be hundreds of years old.

She is very protective of her forest, reacting with hostility to Brendan the first they they met. However, Aisling is also fiercely loyal and supportive once she gets to know and befriend people. She helped Brendan escape his room when his Uncle locked him in for disobeying him, and assisted Brendan in attacking Crom at great peril to herself. So far her only interaction with other characters in the movie is with Brendan and Pangur Ban.

It is also revealed that Aisling can disguise herself into animals such as wolves, deer, and fish. She may be able to become other animals as well, but no evidence of this was shown in the movie. She appears as a salmon in the Origins prequel for Brendan, and appears to be mode-locked to her wolf form by the end of the film. For a short time, however, she appears in her human form when the grown Brendon returns to Kells.