In the tales of the Exile, Lanarak and Londurak are siblings. Farmers and brewers, they’re all but indistinguishable to outsiders, but the two are constantly striving to outdo each other. This mythic pattern remains true today. These holds lie on opposite sides of Mirror Lake, and they’re both devoted to farming and fishing; many of the mountain clans rely on these valley clans for sustenance. But despite their deep similarities in outlook and lifestyle, these two clans are constantly feuding. This rarely escalates to violence, instead typically driving them to find ways to perform better than their rivals, though there have been times where one clan has actively sabotaged the other. Despite this, both Lanarak and Londurak proclaim to possess vast common sense—to prefer fishing to fighting, and to always be able to find a simple solution to complex problems. Dwarves from these clans established inns across the holds; these days, most of these inns have been bought up or licensed by House Ghallanda, but there’s a decent chance that if a bartender’s a dwarf, they’re from one of these two clans.
While Lanarak and Londurak don’t mine metals, both traditionally farm mushrooms and red pudding in deep caverns, and both were drawn into the War Below. Londurak quickly pulled out of the war; they have sealed all passages and forbidden anyone from venturing into Sol Udar. Lanarak still tends its gardens on the upper levels. This has given Lanarak an edge over its rivals, especially as traditional Mror spirits are made with mushrooms. However, Lanarak has also suffered several significant supernatural attacks over the last few decades—outbreaks of the Frenzy and similar threats. It’s rare for dwarves from these valley clans to take risks or to leave the holds, but a remarkable folk hero or sailor could hear the call of adventure.
Source: Exploring Eberron
Laranak’s feud with Londurak is legendary. All dwarves know of the mutual enmity these two clans possess, and it was only with reluctance and gifts from the other clans that the two agreed to work together to present a unified front at Thronehold. Their councilors disagree with each other out of habit and ancestral hatred more than reason. Now, the two clans wage their private war in whatever socially acceptable ways they can, each shifting alliances with the other clans to outplay the other. Clan Laranak favors red and white body paint.
Source: Player's Guide to Eberron
During the Last War, Laranak was closest with Breland.
Source: The Forge of War