@Cyclone I don't think white giants have been forgotten so much as there're plenty of places around the world that they still roam that have simply not been documented by IC posts. There are still plenty around. They are incredibly tough, despite the number that may have been crunched by spooked brush beasts or the like. They might have some plants growing on them at this point, though.
I had actually planned on documenting white giants as a means for distant transportation for those that can climb on top of them and ride them. Given that their patrol patterns are very consistent and chaotic stuff isn't always around, a couple of hain could sit back on one while it takes them to a tribe kilometres away.
As for dismantling them, that's a bit tricky. The first problem is that they were made before Toun even came up with his calligraphy -- they are controlled by artificial souls in a rather temperamental biological frame. Given that Toun used them as a 'fire and forget' creation, he's not really updated them to use Tounic Calligraphy instead. Currently, the hotbed of mortal calligraphy use is with Sularn's Rovaick in Rulanah. Even if the giants had any calligraphy in them, dismantling one would be a delicate and dangerous process that risks breaching the magical siphon within them and causing random behaviour in the local space of reality. Your best bet would be to find a pre-exploded one in the wild somewhere, like the hain that discovered their aluminium bones.
The good news is that Tounic Calligraphy is not entirely cut off because of the above details. Toun sent countless droningbirds all around the globe to look for and spy on godly creatures. They have Tounic calligraphy all over their interiors. They are much easier to catch! However, they are still powered by a small magical siphon that could cause trouble to those that aren't careful.
