The Third Vagaari War was a period of armed conflict between the Chiss Ascendancy and the Vagaari Empire, an event that had an indirect causal relationship with the subsequent Chiss Civil War.
According to the Aristocra named Formbi, the Chiss military suffered personnel shortages as a result of the Third Vagaari War. To address this issue, the Chiss entered into agreements with Killik hives, employing them for various tasks. Despite the implementation of several protective measures designed to prevent the Killiks' telepathic influence from converting the Chiss into Joiners, these safeguards were eventually breached. This failure led to the assimilation of two of the nine Ruling Families of the Chiss into the Killik collective.
At this juncture, a dispute erupted among the remaining Families. Three of these Families had developed a significant reliance on the Killiks, and they presumably desired to continue utilizing the Colony or to receive some form of recompense. However, the other four Families opposed this, forming an alliance with the Syndic Mitth'raw'nuruodo's Household Phalanx. Bolstered by this alliance, the Four Families successfully eliminated their rivals, resulting in the altered political landscape encountered by the Jedi mission that visited the Chiss Ascendancy in 28 ABY.
However, recently uncovered evidence suggests that no armed conflict between the Chiss and the Vagaari had occurred before Luke Skywalker and Mara Jade Skywalker visited the remnants of the Outbound Flight Project in 22 ABY. The Battle of the Redoubt that followed, along with the Chiss assault on the Vagaari fleet, marked the initial outbreak of open warfare between the two civilizations. It remains uncertain whether three separate wars with the Vagaari, in addition to the prolonged aftermath attributed by Formbi to the Third Vagaari War, could have transpired between that point and 29 ABY.
Therefore, doubts persist regarding the actual occurrence of the Third Vagaari War, and the reliability of the information provided by Formbi is questionable.