The Vergulstungwaffen 3, or V3 for short, was a superweapon developed by the Gray Men between the Belkan War and the Circum Pacific War. A further development upon the V2 MIRV warhead, it was unfinished when the Gray Men fell, but its development was completed by the Reborn Knights of Belka, and one of the weapons was shipped to Leasath during the Leasath-Aurelia War. Fortunately, the destruction of Archelon Fortress and the defending Fenrirs prevented this weapon from being used.
In concept, the V3 is a modified V2 MIRV warhead and works in much the same way. However, whilst the V2 was meant to do damage through explosive power, the V3 was a much more sadistic type of weapon; it was designed specifically to use radiation as its primary damage source, with the intent of causing slow, painful deaths of the user's enemies.
Similar to the V2, the V3 is first mounted on an ICBM, then launched into space. Once in space, the warheads split up into seven smaller ones, each one aimed on a different target. However, unlike the V2, the V3 instead carried seven clusters of small tactical nukes, which once near the targets would separate up into the individual, low-yield nuclear warheads and then detonate.
Each warhead would have been "salted" (laced with another metal) with cobalt, which would spread the radiation further and make it last much longer. In the effected regions, besides those caught in the relatively small blast, the first signs of an attack would be communicatiosn being cut off by the EMPs released by the explosions. Next would be symptoms of radiation poisoning; within hours, people would start dropping dead as a result. However, it was those that survived that faced the worst effects: within days, crops would begin to fail, and all water supplies would become contaminated, causing more to die from radiation sickness due to consuming contaminated food or water, causing a backlog at local hospitals. Long-term, the land would take a long time to become fertile again, causing famines in regions that rely on agriculture, and many people would be suffering from cancer; some of them would survive, while others would die. The effects could become so severe that an entire nation's government could collapse under the strain. It's estimated that it would take an entire century for a region hit by a V3 to return to normal.
As it was based on a proven weapon, the V3 is quite feasible. If anything, it's more feasible than the V2 that came before it as a single shot could cause the collapse of an entire nation, allowing a war to be won with a single attack. In essence, this was the V-weapon that the Belkans had been looking for in 1995, for had this been used on say...Ustio, said nation would be brought to their knees, and even if the target were a larger nation like Osea, the target would be crippled by food shortages and refugees flooding into other unaffected areas (which due to the cobalt flakes spread by the V3 landing on these people meant that they would actually be spreading the radiation further, much like a plague of sorts), causing a major economic depression that could last for decades.
On the other hand, like all nuclear weapons, use of the V3 is subject to Mutually-Assured Destruction, and while there hasn't yet been a weapon developed that worked quite the same as the V3, a nation like Osea would have more than enough conventional nukes to cause the same effect as a single V3 strike in retalliation. As a result, the use and effects of the V3 remain purely theoretical.
On another note, the V3 is still more practical than another V-weapon that was developed around the same time, the V-X Antimatter Bomb, as while the V3 is subject to MAD, the V3 doesn't have the potential to single-handedly wipe out all life on the planet, as opposed to its much bigger and much more powerful "brother".