Glyphic fossil is a currency item which has a Corrupt Essence mod effect when socketed into a resonator. It has the same impact as if you would apply either Essence of Horror, or Delirium, or Hysteria, or Insanity. Mind that the effect of essences is chosen in a random way. In the Path of Exile game the price for this one of fossils is 20 Chaos Orb. A player can also buy a POE Glyphic fossil from Niko the Mad or have it dropped in the Time-Lost Cavern of Frozen Hollow in Azurite Mine.