Unicorn Jelly

"Unicorn Jelly is a philosophical science fiction manga strip which tells a metaphoric and purposeful story with a definitive beginning and ending."

Unicorn Jelly is a webcomic by Jennifer Diane Reitz. It starts out as a D&D-esque fantasy story about the adventures of a witch named Lupiko, her adoptive daughter Chou, and her pet jelly Uni. But then it gets very, very weird. Think Homestuck-level weird.

Although the plot is somewhat hard to follow (and the messages it tries to communicate are not very subtle), I found myself incredibly fascinated by the worldbuilding of Reitz's story.

Canmom wrote a really great review of it here. There's also a TVtropes page.