Worm Food is a boss-summoning item used to summon the Eater of Worlds. It can be used at any time of day, but only inside the Corruption.
The End of the Cycle is a event you can get through the Shroud that gives you a lot of bonuses for roughly 50-60 months, before causing all of your inhabited worlds to be destroyed and turned into inhabitable "Shrouded Worlds".
The player must be in The Corruption to summon the Eater of Worlds; moving too far away from the biome during the battle will cause it to flee.
The Eater of Worlds is a pre-Hardmode Corruption-themed worm boss. It is summoned using Worm Food from within the Corruption and Underground Corruption, or by destroying 3 Shadow Orbs that spawn in Corruption-filled worlds.
The Bloody Spine is required for the boss that spawns there, which is the Brain of Cthulhu. It is however still possible to summon the Eater of Worlds in a world that spawned with Crimson by artificially creating a Corruption biome (with at least 300 \ 200 Corruption blocks), and then using the Worm Food within it.
It is summoned using Worm Food from within the Corruption and Underground Corruption, or by destroying 3 Shadow Orbs that spawn in Corruption-filled worlds. It can be summoned at any time of day. Do note that Eater of Worlds shoots vile spit in Expert and Master mode.
Haven't had any trouble, myself. Worm Food is crafted in the 5th tab (from the left). If it's definitely not showing up there, try pressing X while in the crafting menu to toggle the showing of only available items. Think For Yourself; Question Authority.
It is summoned using Worm Food from within the Corruption and Underground Corruption, or by destroying 3 Shadow Orbs that spawn in Corruption-filled worlds. It can be summoned at any time of day. Do note that Eater of Worlds shoots vile spit in Expert and Master mode.
To spawn, the World Feeder only requires the player be considered to be in a Corruption Biome. Spawn surfaces do not have to be Corruption Biome blocks.
Players must use the Screaming Invitation in their map device to fight The Eater of Worlds. The invitation drops after defeating The Infinite Hunger and following the quest steps.