Publisher: Hit Point Press
A standalone 5e dark carnival horror campaign setting and adventure for levels 1–10, centered on a cosmic carnival called the Revelia, run by the entity Heckna. Corruption and forced “revelry” turn victims into thralls.
Heckna! is not native to Exandria: the Revelia was reachable from Exandria as an extraplanar location.
Reference: hitpointpress.com