Orichalcum is a common relic that gives you 6 Block at the end of your turn, but only if you end it without Block. It is a good defense relic, though you always need to take it into account when defending.
But it will work very poorly with After Image, since playing any card will disable Orichalcum
Trivia
Orichalcum is a metal mentioned in several ancient writings, including the story of Atlantis in the Critias of Plato. It was, most likely, a alloy of copper/gold and zinc/tin (granting its green color) and due to the fact that tin was rare at the time, thus justifying its mythical origin/existence.
Update History
Weekly Patch 51: Recursion
Updated relic art for Orichalcum.
Weekly Patch 23: Testing Continues...
Orichalcum now triggers even if Frost orbs trigger. ...
Weekly Patch 21: Channel Lightning
Fixed bug where Orichalcum relic never stopped flashing.
Weekly Patch 9: Ascension
Fixed issue where Orichalcum will start flashing even if you have Block from Barricade/Blur/Calipers.