Toskirakk was not *deep* underground, per se, but it was built into a mineral-rich canyon; beyond the portion you can see were probably areas that did rise above ground level, and perhaps additional mining galleries deeper underground. The Rallosians and many of their slaves were very proficient with magic and probably had a network of portals established throughout the world, which facilitated their subjugation of Norrath. Following the destruction of Toskirakk and the establishment of the Curse, the Rallosian Empire crumbled rapidly and most of their more impressive works (such as the portals) were soon destroyed.

Regarding other bits of lore, I should point out that a) not all lore in the world is going to be 100% accurate or reliable in terms of consistency to begin with due to the fact that not everyone making history in Norrath is completely diligent or truthful as sources of narration, and b) certain aspects of the lore become subject to a shift in perspective the moment many thousands of Norrathians became able to travel back and forth in the timeline...

- Raramor



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