|Source||Magrâbik, possibly others|
Tolm is the densest material on Bal-Kriav. It was created in the Demon Spawn War by members of the Quara'tun Covenant. They fused magic with rune-carved stones as way to channel magic from the Web of Magic. Those that did not last, became fragments that are now both rare and much sought after. Those that remained intact became sources of magical power, containment wards, and the like. A lot of the stuff was used as rings of power around the various gates that were opened in the war; these gates served as a bridge for the demon hordes coming out of the Abyss and besieging the Mortal Systems. Most of the experiments for creating this stone were done in Magrâbik, making this region the predominate source for it.
The next group to make use of Tolm were the Lith-Crillion. They used it to draw enormous amounts of magical power and turn masses of rock into floating islands with all the properties of earth motes. When Miradalêth was sacked by the Thraedli, the eldritch giants acquired an understanding of tolm and its use with creating powerful wards. They put it to use in containing the necromantic energy pouring out of Frosvirk. This containment field became known as the Maen Fyrk Boundary Ward.
A few years after the start of the Thrones War, a special group of Tamlêrran wizards used tolm to fabricate the Magrâbik Monoliths. They created these marvels to serve as anchors for what became known as the Elemantum Boundary Ward.
Tolm is resistant to all magic outside of what it produces. It even temporarily nullifies magic within 100' of it. Tolm has the unusual property of becoming exponentially more dense as it is taken above sea level. As a result, moving the stuff around is difficult, often requiring long treks through the Underdark.