i was just reading the symbols section of delusions and found that someone had posted that they thought the calliach had lived in the dire marsh, and i thought that that was before it had become a marsh and maybe the trow had used the same magic to create the dire marsh out of a calleach homeland as they maybe use to sink the kingdom of yer-ks
also as another theory, iron can make up 5-25% of the earths crust and the calleach knew that the trow had the dream of molten iron, so maybe they used their magic to remove all of the iron from their homeland when the trow attacked so that it couln't be used against them. not calculating the drastic effect it would have, or not caring because they knew they were toast anyway.
and a third possibility is that after the trow conquered the calleach they used all of the iron from their homelands to build cities and arm their warriors, withdrawing the iron from the ground again, by magic, causing the land to lower noticeably.
ps. you can get an approximation of what i mean by iron content in the ground if you go by a river and rub a magnet in the sand and see the iron dust that sticks to it( a river did run through the place where the marsh was so the ground woulds have a relatively high content of iron. this could also be why the gjol is poisoned, because when iron is smelted, many toxic chemicals like mercury and sometimes lead can be left behind and these could linger to poison a river like that for many many years.
Gothmog
