I’m building a D&D world for a game, and one of the major details I really want to include in this world is the Evil Mage and their tower. The tower is a light blue, 3 stories tall, intricately carved, and translucent/partially transparent. I don’t want to change the boxed text I have for it (reproduced here in case it helps), but I want to know if there is a plausible material useable to build it.
The description I will tell the players is:
As you approach the blue structure, you begin to see more details. The tower raises high into the air, taller than the tiny huts surrounding it. Against the gray landscape, it’s almost an impossibly bright shade of blue, just lighter than [one of the characters who has blue hair]’s hair. When you get closer, you can see faint outlines of creatures moving behind the walls. Light passes through easily, but the intricate carvings of dragons on the walls prevent you from seeing too much detail.
I wanted to know, given that it is a setting where magic is limited (but not impossible, because D&D), whether some substance that lets light through, but is strong enough to make a several story tall building, could exist. Specifically, a good answer here should minimize the amount of magical hand waving; I’m perfectly willing to say “magic carved it”, but “magic made it all” is not plausible in the setting (homebrew world, low magic, modern tech), and I would especially like something plausible in the real world if there is such a thing. The technology level is relatively similar to our own world, probably equivalent to 2010 technology or so.
What material could make such a tower?