You can find Mull eggs floating through the air. How do you know it's an egg and not a real bubble? It won't pop when you touch it.
Mulls love to float around the Cave and roam the streets of Ark City, spreading cheer and happiness. Feeling lonely? Have a conversation with a lovable Mull.
Mulls also have an ability called "Mull Mirroring" where they connect you to another person in a different location that is also talking to a Mull. It's kind of like a telephone system! So, people sometimes use Mulls to meet new friends. You never know who you might meet. In order to be able to use this ability, though, you'll need to befriend a Mull and be on good terms with them first.