Operation Gemstone

Operation Gemstone was the codename of an Everian military mission to assassinate the King of the Ironhearts in 1464 ANG and place his son on the throne. It was executed by a small group of elite Everian agents, and serves as a long-lasting, if controversial, example of the power of a few individuals to change the course of history.
Background
While the Ironheart Kingdom had maintained a tenuous relationship with the Baronies of Everflame prior to the war, Emperor Gaulus began forging alliances with Gildmire's other neighbours, especially Litheria, after the discovery of runecraft and the subsequent arms race. When the First Arcane War broke out, he Baronies of Everflame and Gildmire, lacking in allies, lost significant ground in the initial years. With Thandorth lost and Bergen's Keep under siege, significant pressure was placed by Gildmire on its allies to do something drastic.
Impressed by Litheria's acquisition of the Orcish Nomads as allies and several failed assassination attempts, Everian generals looked for an opportunity to do the same elsewhere. Political strife in the Ironheart Kingdom made it an ideal target, though early plans of a destabilisation mission to provoke a civil war were altered when it was discovered that Benin Gaulus, the current king's eldest son, was vastly in support of the Alliance of Kings.
Preparation and Execution
A team of 5 agents, whose names have never been declassified, were selected and outfitted for the mission. Notably, this operation was the first military use of Henrich's amulets of communication, which enabled the team to co-ordinate timings with extreme precision. 
On the 15th of Newdawn 1464, the team was teleported into the Ironheart Kingdom, as close to Thronehold as its anti-teleportation countermeasures allowed. After another 23 days of hiking, they arrived at the city, using a combination of magic, stealth, and guile to either infiltrate or sneak into the Mountain Palace. No Everian records exist of the operation, but the Dwarven autopsy concluded that the King had been incinerated by an open furnace. Due to the lack of intact remains and the preoccupation of the Kingdom's clerics with the war, no sufficiently powerful cleric was available to bring him back to life before his son took the throne.
Aftermath
Just a day after he ascended to the throne, Benin Gaulus called for a ceasefire with Gildmire, and, on the 7th of Greenspring, officially joined the Alliance of Kings, beginning a new offensive on Litheria's western border. After the war, international Dwarven relations improved significantly, even after the dissolution of the Alliance of Kings a century later. 
Few of the general public are aware of the operation, though public records exist in the Central Libraries of both Everflame City and the Great University. Most who do know are indifferent, seeing it as ancient history, though a dwarven extremist group known as the Children of the Earth uses it as one of its many reasons for opposition to both Everflame and the current Ironheart government.
The operation is also pointed to by historians and theologians as an example of the 'Hero Effect': how, given enough instability and centralisation of danger, a small group of individuals can affect world-spanning change. Considered an oddity by some, an inevitability by others, and evidence of the existence of the New Gods by a few, the phenomenon has been seen through many periods of Tilendrel's history.