In classical myth
Ichor originates in Greek mythology, where it is the ethereal fluid that is the Greek gods' blood, sometimes said to retain the qualities of the immortal's food and drink, ambrosia or nectar. It was considered to be golden in color, as well as lethally toxic to mortals. Great demigods and heroes occasionally attacked gods and released ichor, but gods rarely did so to each other in Homeric myth.
Iliad V. 364–382
Blood follow'd, but immortal; ichor pure,
Such as the blest inhabitants of heav'n
May bleed, nectareous; for the Gods eat not
Man's food, nor slake as he with sable wine
Their thirst, thence bloodless and from death exempt. †
† We are not to understand that the poet ascribes the immortality of the Gods to their abstinence from the drink and food of man, for most animals partake of neither, but the expression is elliptic and requires to be supplied thus—They drink not wine but nectar, eat not the food of mortals, but ambrosia; thence it is that they are bloodless and from death exempt.
In Ancient Crete, tradition told of Talos, a giant man of bronze portrayed with wings. When Cretan mythology was appropriated by the Greeks, they imagined him more like the Colossus of Rhodes. He possessed a single vein running with ichor that was stoppered by a nail in his back. Talos guarded Europa on Crete and threw boulders at intruders until the Argonauts came after the acquisition of the Golden Fleece and the sorceress Medea took out the nail, releasing the ichor and killing him.
In pathology, "ichor" is an antiquated term for a watery discharge from a wound or ulcer with an unpleasant or fetid (offensive) smell. The Greek Christian writer Clement of Alexandria used "ichor" in this sense in a polemic against the pagan Greek gods.
H. P. Lovecraft often used "ichor" in his descriptions of other-worldly creatures, most prominently in his nightmarish detail of the remains of Wilbur Whateley, in The Dunwich Horror. Author Ursula K. Le Guin, in From Elfland to Poughkeepsie, calls the term "the infallible touchstone of the seventh-rate."
In the video game Warframe, the weapon "dual ichor" is a pair of two short blades that do poison damage to foes. Considering all foes are mortal, it fits rather well.
In the video game Terraria, ichor is a loot drop from Ichor Stickers and Tainted Ghouls and is used to make various items that inflict a unique debuff which lowers defense by 20, regardless of armor type.
In the manga Immortal Rain, ichor is an injection created by the character Yuca that suppresses the mutation of angel blood in the series.
"Ichor" is the name of a Death Metal band.
In the video game Shovel Knight, ichor is a special liquid that can be filled into a chalice by the so called Troupple King. These liquids have special effects when used, being able to heal the character, grant him immunity, or attract treasures.
In the novel "Police Ladies" by Yolanda Celbridge, ichor is a mixture of bodily fluids which the main characters drink in a pagan ritual with sado-masochistic overtones. 
- Of uncertain etymology; R. S. P. Beekes has suggested that is a foreign word (Etymological Dictionary of Greek, Brill, 2009, pp. 607–8).
- Homer, (trans. William Cowper) (1802). Johnson, John, ed. The Iliad of Homer, Translated into English Blank Verse. Volume 1. Iliad V. 364–382 (p. 153).
- ichor - definition of ichor by the Free Online Dictionary, Thesaurus and Encyclopedia
- Ursula K. Le Guin, From Elfland to Poughkeepsie, p 80 The Language of the Night ISBN 0-425-05205-2
- Butcher, Jim, "Cold Days", Chapters 6 & 23 ISBN 978-0451419125
- The dictionary definition of ichor at Wiktionary