Book of Grudges
The Great Book of Grudges (Dammaz Kron in Khazalid) is a sacred item to the Dwarven folk.
In essence, it's pretty much the place where they record 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 them (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, we mean AN AXE TO THE FACE. Alternatively, since Thorgrim is not fucking retarded like most of the other Dwarf kings before him, he lets 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. Additionally: if we can take a loading screen image from Total War: Warhammer as canon (but it would be in character for them to do so), they are not above declaring grudges against mountains, literally, for a landslide or something that killed some dwarfs. Such a grudge would be settled by strip mining the shit out of the place until nothing useful is left.
When a grudge is settled, it is crossed out. Of course this being Dwarfs, until Thorgrim came along grudges were rarely crossed out even after they were avenged because most Dwarfs consider it more fun to reminisce about the vengeance. In addition, more grudges appear than are settled as each battle means dead Dwarfs or injured equipment, which means more grudges as a cycle of revenge. 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.
Surprisingly, despite all these grudges, you never hear about a Dwarf Book of Grudges running out of pages. Lore implies that at least the High King's book magically either has an endless number of pages or generates more when needed; it's confirmed that the magic allows it to remain the same size and weight no matter how many pages it has.
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 when the vampire escaped with her, Tyrion blamed the Dwarfs for it and insulted them so offensively it was as if he physically struck them. 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. He also didn't want to perpetuate the vicious cycle of vindictiveness. This also shows that Grudgebearer is actually cool-headed for a Dwarf.
List of notable "Extraordinary" individual recorded in the book
Skarsnik - The one mention having the most entries in the book. A cunning goblin as well as the warlord of the Eight Peaks. Congrats, you filthy grobi, hope Griminir feasts on your dirty greenskin blood, you little shit.
Grimgor Ironhide - Committed several acts of dawi-slaughter with his magic axe Gitsnik, as well as cooking captured Dawi alive inside their armor.
Neferata - The first undead on the list. She invaded and conquered a Dwarf hold, The Silver Pinnacle, and thus began the Dawi hatred for undead.
Malekith - Broke Snorri Whitebeard's promises and caused massive devastation on both elves and dwarfs after he disguised his agents as high elves to assault a dwarf caravan. Apparently has so many grudges against him that a complete record outside the page-generating Book of Grudges would fill libraries (yet still not as many as Skarsnik the aforementioned goblin, who is much younger than Malekith, mind you). Fuck Malekith, you Elgi'drazh piece of shit!
Queek Head-Taker - Killed many dwarves during his fight for the Karak Eight Peaks as well as wasted an entire armory of expensive, powerful runic weaponry at Karak Azul in a pitch battle where he tricked the Orc of black crag to fight with the dwarves of Karak Azul. This grudge got redeemed in the End Times where Queek was publicly beheaded by Thogrim with his axe during the Skaven siege on Karaz-a-Karak.