The Ancient Herald is a boss monster that spawns during the Aporkalypse.
It attacks by diving into the ground, emitting a shockwave that destroys structures. In addition, it will periodically summon various creatures and attacks to help it. It can summon either 4-5 Pig Ghosts, 4 Nightmare Creatures, 2 Meteors, or a lot of Poison Dart Frogs.