Ichor is a Hardmode crafting material which is immensely useful in getting started after defeating the Wall of Flesh. Found by killing certain enemies in the Crimson Biome, this material is useful in extending your arsenal to having higher damage as well as inflicting the very powerful Ichor debuff.
How to Get Ichor
Ichor is dropped by Ichor Stickers in the Underground Crimson Biome, Tainted Ghouls in the Underground Crimson Desert Biome, and can also be obtained by opening Hematic Crates. These crates are fished up in the Crimson Biome in Hardmode and can also drop a number of other useful items like Souls of Night and Hardmode ores.
Farming for Ichor
While Hematic Crates may seem enticing, they are relatively rare and don’t always have useful drops. Hardmode ores are more easily obtained by opening Pearlwood, Mythril, and Titanium crates instead, and Ichor Stickers have double the drop rate of the crates.
The best idea is to simply farm enemies in the Underground Crimson, as the Feral Ghoul also has a low drop rate for Ichor. As well as killing Ichor Stickers, you will be able to kill other enemies such as Crimson Mimics which drop powerful Hardmode weapons and accessories, as well as every enemy dropping Souls of Night for other crafting recipes.
While useless on its own, Ichor is an excellent crafting material and is able to make items that will help you get past the initial difficulty spike in early Hardmode. Some items even stay relevant all the way to the endgame due to the power of the Ichor debuff. This debuff lowers an afflicted enemy’s defense by 15, increasing damage output no matter what you hit it with. Items Ichor can be used to craft include:
Golden Shower: a spell tome which spews a dubious stream of ichor and deals damage to enemies while inflicting the Ichor debuff for 10 seconds. It can be crafted using a Spell Tome, 20 Ichor (30 on 3DS), and 15 Souls of Night at a Bookcase.
Ichor Dart: ammo used in the Blowgun, Bowpipe, Dart Pistol, and Dart Rifle. They inflict the Ichor debuff for 7 - 14 seconds upon hit and will split into two to three smaller darts shortly after firing. They can be crafted by hand with one Ichor.
Flask of Ichor: a flask which grants the Weapon Imbue: Ichor buff for 20 minutes (15 on 3DS) which causes all melee and whip attacks to inflict the Ichor debuff for 10 - 19 seconds. It can be crafted with one Bottled Water and two Ichor (five on 3DS) at an Imbuing Station.
Ichor Arrow: ammo used in bows and repeaters. They inflict the Ichor debuff for 10 seconds upon hitting an enemy but are not recoverable after use. They can be crafted with 150 Wooden Arrows (35 on 3DS) and one Ichor at a Mythril or Orichalcum Anvil.
Ichor Bullet: ammo used in guns. They inflict the Ichor debuff for 10 seconds. They can be crafted with 150 Musket Balls (50 on 3DS) and one Ichor at a Mythril or Orichalcum Anvil.
In a Nutshell
Ichor is a crafting material dropped by Ichor Stickers in the Underground Crimson Biome. It can be used to craft a number of different weapons and ammunition which all inflict the Ichor debuff. The Ichor debuff reduces enemy armor by 15, causing an effective increase in all damage while the enemy is inflicted with it.
Q. How do I get an Imbuing Station?
A. The Imbuing Station is sold by the Witch Doctor for seven gold. To obtain the Witch Doctor, simply defeat the Queen Bee boss found in Hives in the Underground Jungle. He will then move into unoccupied valid housing.
Q. Are any enemies immune to the Ichor debuff?
A. Yes, lots! The important ones who are immune are the Ancient Cultist, all of the enemies spawned by the Ancient Cultist, the Flying Dutchman, the Paladin, the Solar Pillar, and the Destroyer. It should be very effective on almost all other enemies though.