The Aporkalypse is a Solar Eclipse that happens when all three sigils on the Aporkalypse Calendar align. Without player control, this happens on the start of the 61st day in a Hamlet world. During this event, the world and any light sources are tinted red, and it becomes night. Many creatures and aspects of the game change, getting much more difficult.
- Seasonal effects still occur, such as Hay Fever and Fog. There will no longer be any day or dusk periods, only night. The BFB will not spawn during this time, and if summoned, will land and take off immediately.
- All shops become locked, as per usual for nighttime. However, Royal Guards will no longer patrol, and will stay inside at all times. They can be knocked out of their house by a hammer, but the Worker Pigs will not repair any damaged structure.
- Many creatures have their behaviors changed.
- All Mants hatch into Mant Warriors. The new Mant Warriors now glow, emitting a small amount of light that spreads across a large distance. Any new Mants spawned by the Antcomb Home automatically turn into Mant Warriors.
- Pogs also have their appearance changed, becoming feral and ragged, attacking the player and any creature on sight.
- Pikos and Orange Pikos turn rabid.
- Iron Hulks are perpetually activated, and do not deactivate.
- Vampire Bat attacks become much more common and much more severe, happening every 'night', or the time that would have been nighttime. The amount of bats that spawns is greatly increased. It is able to find upwards of 10 Vampire Bats spawning if the player activates the Aporkalypse on Day 1. The bats will circle less, tending to rush the player.
- Elder Mandrakes become neutral, their facial expression changes from a frown to a smile, and they can be befriended with raw Vegetables.
- Anywhere from 2-5 Ancient Spirits spawn in every room of every Ancient Pig Ruins. If all ghosts in the room are killed, new ghosts will spawn when the player returns to the room.
- The boss monster Ancient Herald spawns shortly after the Aporkalypse begins. If killed, it will respawn in a short time. It currently does not drop any loot.
This event is treacherous, with perpetual night, many many bats, allies turning into enemies, and constant threat of the base-destroying Ancient Herald. Unless the player wants to farm Pig Skin from the Vampire Bats, or a drastic difficulty increase, avoiding this event by using the Aporkalypse Calendar is recommended.