This is a common drop from all mobs in the Abyss.
In addition to the quests listed (one for each race) that give you your initial supply of 300, the only way we are certain of to get more is as drops from mobs in the Abyss.
During Beta there was a merchant in the same room in Sanctum where the Stigma Master is found, but we have not confirmed that the merchant is still there and have not found one in Pandaemonium. The Stigma Merchant may have been only for Beta.
This page last modified 2010-12-03 22:37:52.