Cale Tucker said
ASTA, how would theVul'kruun react to the Esurienti? In space and on their planet (not a hove, just some of them ahot down onto the planet)
They'd slaughter everyone and consume the dead bodies.
When dealing with vul'kruun, it's imperative that one takes heed of their inhuman psychology. They have difficulty in coming to rational conclusions. Additionally, they cannot register alien vocal, chemical, acoustic, or bodily language very well because vul'kruun communication is all that they know; their strong instinctive urge to flag other sapient life as prey and would-be foodstuffs doesn't help either, and their inherent aggressive demeanor and fierce opposition to territorial encroachment makes things worse for civilizations that may want to contact them for whatever reason. Coming to them with open arms and proclaiming your peaceful intentions is a terrible idea in all honesty, because they'll probably perceive it as an immediate threat and react to it accordingly.
Here's an alternative: Use sufficiently-advanced technology. Vul'kruun have excellent skill with harnessing the potential of the atom despite being a species that's currently experiencing their technological equivalent of the [1950s-1960s] Atomic Age, while their weapons technology exceeds that of modern and near-future Earth. However, their computing prowess is lacking in the digital department (they use sophisticated analog computers and fiber optics, which makes them immune to EMP weaponry--something that was a strong asset on a planet plagued with cosmic radiation, frequent solar flares and nigh-eternal nuclear warfare), so they don't have much in the way of 'universal translators' or other apparatuses that would make dealing with a foreign people easier.
Or, you can go with AlienBastard's route and lure the vul'kruun's murders (the term used to designate one of their 'fleets' or 'squadrons', though squadron is probably more accurate because their spacecraft are not modeled after traditional space-capable maritime vessels) into assaulting someone that you don't care for.
If pointless warfare isn't your thing, I can always handwave a few things and say that a vul'kruun tribe found itself separated from the main species mass. Strange generic and neural engineering probably saw them take on a cooler and more rational temperament.