“It is said that, in the ages before the coming of man, an ancient race practised an even older magic. Knowing not the ways of the scroll and grimoire, these peoples stored their spells in large rectangular standing stones known as ‘taypes’ in the ancient tongue.
By the time of the founding of the great magical city, these folk and their stone ‘taypes’ had vanished into legend – a legend that drew many a wizard into the great icy wastes that lay leagues to the north of their home, where scattered stones could still be found.
However the wizards knew not how to transfer their magic into these stone tapes (as the common tongue had corrupted the term). The stone would not absorb their magic and resisted the chisel of even the most skilled stonemason. However the wizards discovered that a portion of the stone tapes’ great capacity could be tapped into by writing their spells onto the surface (cat’s blood was thought to be the most efficacious medium).
Further storage could be attained by lining the stones in a row, it was believed, and thus the great libraries of Felstat became lined with row upon row of these ancient monoliths, brought back to the city by great and perilous expeditions to the wild lands.
It is said that, deep under the ice, row upon row of these stone tapes still stand erect like giant guardians frozen side by side; broken, faded, yet still steeped in magic as ancient and arcane as the First Times.”
Neelnygellicus (972) Customes and Practices of Olde Felstat Vol III: Ulfenhalle College of Magick Press
In other words, I hacked some bits of foam packing into rough rectangles and painted them in my now standard stone colour scheme for some cheap, quick and easy terrain.