The Malfa War

Early in Malfa's history—after its establishment as a permanent trading town, but before The Deeping was built—there was a conflict between those Maveren who lived permanently in Malfa, and those who were still overseas. The overseas Maveren saw no reason for the Malfa Maveren to control the trade themselves; what started as what's-yours-is-mine raids escalated into a war.
The overseas Maveren laid siege to Malfa, briefly occupied it, and then were repulsed. The resulting agreement left Malfa's founding Houses as the only ones with claim to Malfa, its territories, and its trade. It is commemorated by the Spear, a war monument in the Grand Plaza; the Spear is sometimes referred to by non-Maveren as the Maveren's Needle Dick, but not where Maveren can hear.

The split Houses

The Malfa War was mostly fought between different Houses, which then became known as the Malfa Houses and the Sea Houses. However two Houses were split down the middle during the war, with members on either side.
Grimmvatten mostly sided with Malfa, but a minority took the other side. Many Grimmvatten on both sides died during the war; afterward, both sides claimed to be the real Grimmvatten House. The overseas Grimmvattens were few, and eventually died out; the Malfa Grimmvatten rebuilt by adopting more new members than many Houses do, including more humans than some other Houses consider wise.
Vattn House is the only founding House of Malfa with no remaining claim on the city. Vattn is and has always been a Sea House; only a small number of its members sided with Malfa. During the war, they took the name Valdas, after the then-seniormost Vattn in Malfa. After the war, Valdas House as an independent entity was made official by a vote in Summing; the Sea Houses acknowledged it as part of the peace agreement.
Vattn was famous for the power, arrogance, and occasional cruelty of its members; it is generally thought that those Vattn who founded Valdas were the most arrogant members of the most arrogant House of the naturally arrogant Maveren. There were never many Valdas, and when the last members left Malfa for parts unknown, they weren't widely missed.