From the Wizard101 website:

Beastmoon Hunt Event!

"Unleash your inner animal! Now through Monday, October 10th, don a beast form and get ready for the hunt of a lifetime during the Beastmoon Hunt! Join a team and battle other Wizards in a limited-time game mode to earn incredible rewards! Learn More "

See the Announcement here:

See additional information here: Basic: Beastmoon Hunt

And see the additional information posted by @Pegasus Unbound here: A Basic Guide and Introduction to The Beastmoon Hunt