RPG Adventure: The Hole in the Oak

Details
A hole in an old oak tree leads characters down to a maze of twisting, root-riddled passageways, the chambers of an ancient wizard-complex, and the banks of an underground river where once a reptile cult built their temples.
Come see an adventure that's what the old-heads say the good old days were like, but with plenty of good modern-day design sensibilities.
Have an adventure in the realm of Dolmenwood, a fantasy world inspired by British folklore and all the eerie fae mystery that implies. We will provide pre-made level 1 characters, using the Old School Essentials system. If you're familiar with D&D 5e or any d20-based system, you will already know a good chunk of how everything works. Those who aren't, don't worry; the rules are actually simpler than a lot of modern RPGs.
If you've played The Hole in the Oak before, you're welcome to play, but be sure not to spoil any secrets :P.

RPG Adventure: The Hole in the Oak