The Ichor Sticker is a Hardmode enemy that spawns in the Underground Crimson and floats around in the air. When tracking a player, it spits a stream of Ichor at them similar to the Golden Shower's. The stream inflicts the Ichor debuff, lowering the player's defense by 15 / 20. Upon death, Ichor Stickers will drop Ichor.
To easily farm Ichor, it is recommended for the player to create horizontal shafts in the Underground Crimson for the Ichor Sticker to spawn. A three-tile tall shaft will cause the Ichor Sticker to become stuck and barely able to shoot the player (as they shoot in an arc); with a four-tile tall shaft, they become mobile but will still have problems shooting the player. The player will also have more room to deal with the irritating Floaty Gross, which can fly through blocks.
Ichor Stickers appear to sink in any liquids they enter and can be effectively immobilized by water that is at least four tiles deep. While this will not prevent them from shooting if the player is in sight, they can be easily dealt with using nearly any weapon available at the start of Hardmode.
A common mispronunciation of "ichor" is /ɪ-kr/ or "icker", which would make the Ichor Sticker's name a rhyme; however the correct pronunciation is /aɪkɔr/ or "eye-core".
The Ichor Sticker is the only enemy with a ranged attack in both the Crimson and Underground Crimson, and it also has the highest maximum health of all non-boss enemies in both biomes.