From the publishers blurb:
This Campaign Drop is designed for character levels: 5th to 10th. It features
a dragon’s lair with a fungal Green Dragon served by Chaotic Mycelian
cultists and other fungal dangers. It is high risk, high reward.
Campaign Drops are setting neutral locations and short adventures designed for instant inclusion in your campaign. This Campaign Drop is compatible
with Old School Essentials and other Retro-Clones of B/X gaming.
Amanitus the dragon presents for an unusual challenge to your players.
While some players might be familiar with the basic abilities of a Green
Dragon, this is an ancient wyrm. He’s developed a few unique capabilities
and gathered a few followers along the way. His lair is hazardous too. Taken
together, the adventurers face a dangerous challenge.