The explosion of a star caused by a Conversion Weapon; this particular type of artificial supernova is classified as Class IV
Monopole based self-replicating weapons sometimes used to detonate stars.
Generally employed at the S3 level or higher, conversion weapons normally operate by injecting one or more self-replicating monopolium factories into the outer layers of the target star. Since the factories are themselves constructed of monopolium, they are able to operate deep beneath the stellar surface and use the large energy and mass gradients there to replicate at extreme speed. A monopolium factory or other device required to operate in a sub-stellar environment is typically supported by buoyancy; a very thin shell of dynamically supported monopolium surrounds a large vacuum chamber, and by this method the density of the entire device can be adjusted until the device floats. Typically it takes no more than 24 standard hours for a conversion swarm to reach critical mass, and attacks employing multiple starter units can achieve criticality even faster.
When sufficient replicators have been produced, the entire swarm injects itself into the stellar core and breaks up into multiple fragments to maximize reaction area. Within the enormous temperatures and pressures of the core, electromagnetic repulsion is overcome and protons are forced into contact with the magnetic monopoles which convert them instantly into energy. While under normal circumstances only a tiny fraction of the stars mass is "burned" in any given moment, the presence of so many monopoles induces a runaway reaction which results in between 10 and 30 percent of the stars mass being converted to energy all at once. Pressure and gravitic attraction are both overcome and the star literally explodes, releasing an enormous radiation and particle pulse that effectively vaporizes all mass in the star's immediate vicinity and threatens surrounding star systems out to a distance of many light-years. Proximity to such "Type III supernovae" has resulted in the collapse of at least 12 (admittedly minor) civilizations in the last 5000 years and led to calls for a formal ban on the use of these devices. Rather ominously, the archai have refused to support or enforce such a ban, saying only that the use and control of such devices is a matter to be handled on a case by case basis by the "proper authorities".
Modosophont and low transapient level polities have occasionally attempted to use non-replicating conversion weapons to either destroy or disrupt stellar processes for military or political advantage, but such attempts have usually been of limited effectiveness and almost always have caused more problems than they solved. In almost every case (the war against the Amalgamation being a notable exception) the use of such weapons has eliminated virtually any claim to moral superiority that the attacker may attempt to make and often results in attacks on the attacker by surrounding polities or even the intervention of greater powers (up to and including archai level minds) to "restore order".
On a more practical note, lacking the ability to produce self-replicating monopolium devices, a would-be stellar demolitionist must amass an enormous number of monopoles by more conventional means and then transport them to the intended target. Performing both tasks undetected and unopposed has proven to be an unwieldy challenge, and in the modern era, most cultures see no point in the creation or maintenance of such deadly devices. Smaller level conversion devices, such as boostbombs and stellar flare generators are a common part of most arsenals but require far less effort to construct and are far less destructive. Although technically operating on the same principles as stellar class weapons, they are rather like a match compared to an atomic bomb.
For now and into the foreseeable future, conversion weapons seem likely to remain "weapons of the gods".