Book of Grudges
The Great Book of Grudges is a sacred item to the Dwarven folk, and pretty much the place where they keep all the grudges against everyone and everything that ever extremely wronged them.
The book itself came into being since the time when the Dwarfs came into being, and was since then passed down from High King to High King, with the current one being Thorgrim Grudgebearer.
Whenever someone did something really horrible, like hiring them to build a palace then refusing to pay them, or attacking a trade cart killing dozens if not hundreds of Dwarfs for no reason other than you didn't like the (and not stealing a keg of beer for example), then that person's name/group's name/army's name/or even race's name would go into the book with the description of the grudge-worthy act. The good old Dwarven tradition is to settle these grudges the old fashioned way. And by old fashioned, read: A AXE TO THE FACE. Alternatively, since Thorgrim is not fucking retarded like most of the other Dwarf kings before him, he let's the act go if they make up for it, like actually getting paid for that palace they didn't get paid to build, even if it is very late in coming.
When a grudge is settled, it is crossed out. Of course this being Dwarfs, more grudges appear than are settled, and due to what's going on in the Old World, these grudges will dramatically grow in numbers.
It is also said that the more of these grudges fill the book, then the Dwarven race is more probable to die out...unless they actually overcome their stubbornness.
There was however one situation when a grudge was not written down. When the Dwarfs under Thorgrim Grudgebearer's command met with Tyrion in order to save the High Queen's daughter from Mannfred von Carstein, yet Tyrion blamed the Dwarfs for the Vampire Count recapturing her. After this the bearded powderkegs urged Thorgrim to write what Tyrion did into the book, yet the High King chose not to, probably seeing it that they might have screwed up. This also shows that Grudgebearer is actually coolheaded for a Dwarf.