On the surface, the Tîrbalzôn volcano is southeast of the Core Sea. It continuously smokes from hundreds of vents, all scattered about the mountain slopes. Most of the activity comes from three smaller cones that surround a dormant central cone. Tîrbalzôn is an active volcano; just not fully active. The volcano is powered by the Heki Hrolmir; an artery of the Great Vein of Surtur.
Tîrbalzôn has even more dormant and dead chimneys. Some of these descend all the way into Underdark sector Riwthor. These are often steep or near vertical descents; limiting their use to bats and other flying creatures. A few of these vents connect with Balanosas Navel. This network of hewn passages and chambers serves as the labyrinth for vampires. Most of them are former mortal Forstneblin that once got their sustenance from the Quellestir forest. They are known as the Drinkers of Tîrbalzôn; more formally called the As'lith Zybis, a Blood Cult of Kezgihr. This vampire cult came to power in the Core Offensive when a few desperate and dark gnomes were approached by agents of Hlotho Zîn. Some of them willingly accepted vampirism, while others were turned and sent out to "recruit" others.