A Whollyday occurring on the first Sunday after the first full moon after the vernal equinox in the northern hemisphere. Or it happens on Easter.
According to the Mythics of Harmonia, the holyday celebrates the Goddess Erister (Eris-sister) aka Aneris aka Harmonia. While it's called Easter by th Unified Catholic Church, the Baptism World Allegiance calls it Reserection Sunday in recognition of the body of Yeezus hanging flaccid on the cross and then, in three days after angels rolled his rock, rising.
To many Discordians, the primary purpose of Erister is to have an Erister Egg Hunt, also known as EggGASM, as provided by the Erisian Bunny aka Erister Bunny. This consists of placing small items and/or Discordian-related quotes and memes inside plastic eggs to be hidden on or near (often slightly before) Erister.
Erister Bunny (Erisian Bunny)
Called the Erisian Bunny by the Sacred Chao Ranch, the Mythics of Harmonia named the rabbit the Erister Bunny. The bunny is a púca or pooka, a mischievous creature that is a bringer of both good and bad fortune. This is represented by the different types of messages and items found in the Erister eggs. The pooka rabbit is also known as "Harvey."
Erister Egg Hunt (EggGASM)
An Erister egg is a plastic egg into which something unexpected, particularly an odd or surprising message, is placed. It is then hidden to be found much as Easter eggs. But in an Erister Egg Hunt, or EggGASM, the egg finders usually don't know they're participating. They think they're finding normal Easter eggs.
One Easter, the Sacred Chao Ranch Cabal hid plastic Easter eggs all over the mall, supermarkets, museums, churches, etc. that had enlightening fortunes trapped inside. The fortunes were along the lines of 'This is an unfertilized egg', 'The PA lottery number for 5-23-97 will be 17-32-5', 'You picked the 10 of Clubs', '25 cents off of LUCKY CHARMS', and 'You are pregnant (replace egg if you are a man).'
Eleven days before Easter in 2008, the idea was revived or reinvented by Pinky McFatfat of Dubln who announced it with a post on 23ae.com. The practice was called EggGASM by Professor Cramulus and adopted by Black Iron Prison as part of Omgasm, and by Mythics of Harmonia who called it Erister Egg Hunt. In addition to those groups, Shamlicht Kids Club and the Discordian Division of the Ek-sen-triks CluborGuild participated that year. Items that were hidden in plastic eggs that first year included odd quotes, one line meme bombs, a small doll's arm, a pair of black thong panties, a condom, and even a genuine Purple Heart medal. Messages were often included in an egg with a small toy.