For the full story, read through the first forty or fifty pages of the main thread.
The short version is; Terenos d'Avistral.
The slightly less short version: Terenos was sent on a diplomatic mission to Preston and Miring to negotiate trade links and assess their military capabilities. Whilst as a guest of honour in Preston, Terenos discovered that Preston had seriously built up its forces and was planning an attack on Miring; an attack during which half of Miring's nobility would turn on their King and help win the war. Terenos escaped Preston (whilst starting a fire and escaping from it by swinging out of a window on a flame-retardant curtain) and took a round trip to Miring to avoid being detected. This is when he lost the first regiment under his command to bandits. Three men escaped with him to Miring, where he attempted to get an audience with King Leuki von Trubaldsome. One of the nobles attempted to kill him, failed, and after further shenanigans Terenos reached the king's council chamber and delivered the evidence proving the corruption of the nobility. Half the council then murdered the other half, a terrible melee broke out and by the end the only two left standing (not counting Terenos' faithful companion Manning, who had been injured in the battle) were Terenos and the King.
Terenos proceeded not to kill the King and try to seize the throne but instead to pledge alliance from Elbreth in exchange for very favourable peace terms - their plan being to use this as a casus belli to attack Preston with combined forces and expand Elbreth's territory to twice or (if they betrayed and absorbed Miring) thrice its size.
The even longer version is the same, but includes a concealed backstory about the second Trubaldsome child, banished years ago when his elder brother failed in an effort to kill him and spending eight years in an elaborate plot of revenge and an attempt to seize both the thrones of Miring and Preston for himself (to which he would indeed have been the legal heir once Kings Leuki and Philip and Prince Karl were dead). This plan came close to fruition before Terenos cut his head off in his first act of technical regicide (since the throne had passed to him as soon as he had killed his brother).
Edit: King Erik just has a flesh wound, the bolt failed to even crack the skull on such a glancing blow. Bandage and compress and not banging his head for a few weeks and he'll be fine. Probably get a scar, though.
Edit 2: Taric's remaining forces (and Taric) will arrive a few days later. Slightly too late to contribute to this battle, unless they fight to a draw or lose and the defenders don't go on the advance. I rolled to see if your men would obey your order, and then how they would interpret it. A '5' would have been "camp around the castle until Taric arrives, then rush it with superior forces". '6' was "kill the traitor now!"