From the Journal of one Wigmar Heck, pt 40 (Second Battle of Karak Azgaraz)

 

2 Jahrdrug 

It is clear that we will have to remain to defend the dwarfs. If we leave and the orcs come back it's game over for them. I've dispatched letters stressing the need for reinforcements. I've also taken the opportunity to write my Adler associates. If war comes to the Reikland and beyond we must be ready.

3 Jahrdrug 

Ankh's situation is much improved. He's no longer the lethargic man waiting to die. He's back to his old self and it pleases me greatly. It is strange though - he seemed so certain he would soon die and that we would meet again when he was reborn. And I believed him. I guess even Ankh cannot foresee everythig.

5 Jahrdrug

The orcs came in force today. A vast horde of orcs, black orcs, goblins, and wolves. They even brought some trolls. We fought them as they came up the causeway. In their hundred they rushed at us and we shot them dead. Even their black orc shield wall could not stand against ball and canister. The trolls caused some trouble but we dealt with them as well. Before the end of the day a thousand or more greenskins were added to the piles of dead. Surely we have slain more than two thousand by now, maybe more.

We suffered casualties, but again not more than we can handle. We are, however, running low on shot and powerder. We could repel another assault like this, maybe two. But if then thousand comes we will run out and be undone.

6 Jahrdrug

There is a blizzard. Strong winds, heavy snows. The dwarfs say it could last a day, two days - or ten. Impossible to tell. While the blizzard lasts no orc assault can take place. 

The Doomstones

I have spoken at length with Diirk's father, Faust Wife-stealer, the Runemaster. He's one of few elders to have survived the orc onslaught - the loremasters were all slaughtered in the Hall of the Ancestors.

From what I understand the Zul character wielded a powerful artifact of his own: the Stone of the Earth. The one I found is the Stone of Fire. Two more the dwarfs made in the elder days, before the War of the Beard, and together they grant master over the four elements. Each stone is powerful on its own - and also dangerous to the wielder - but when brought together their power grows even greater. If all four gems are united there is nothing their master cannot do. 

How or why the dwarfs of old made these stones - fit for use by wizards and sorcerers - no one could say. Seems the height of folly to me. Dwarfs probably figured that out too, because they split up the stones - now called the Doomstones - and scattered them far away from each other.

One stone resides beneath Karaz-a-Karak, the great dwarf hold in the World's Edge Mountains. One was given to the elves for safekeeping. These are the stones of air and water, though there are no records of which is where. The stone of fire was sent to the far north - how it ended up in the Grey Mountains is not known. The stone of earth was carried to the west, perhaps to the Grey Mountains, to Karak Kulgan. It's now in Zul's possession I believe.

Zul is clearly trying to get to the rest of the stones. or the one that's accessible to him - the fire stone. A single wizard has no hope of breaching Karaz-a-Karak or making it to Ulthuan.