The obsidian cape can be bought from the weapon shop of TzHaar City for the price of 90,000 Tokkul. It is made from slivers of interlinked obsidian and enchanted with TzHaar magic, like all TzHaar equipment. It is one of the two only TzHaar items whose name isn't in the TzHaar language, the other is the fire cape. It is also dropped by the inhabitants of the underground volcano city of TzHaar. Since the TzHaar shops update on 15 December, 2009 it is no longer possible to sell this to the TzHaar shop.
Due to its lack of requirement to wear and useful style bonuses (slightly lower than a cape of accomplishment, or Ardougne cloak 4), it is a popular cape amongst low to medium levelled players.