Blackfyre Rising takes place in George R. R. Martin’s “A Song of Ice and Fire” setting, roughly 120 years before the events of the books. No knowledge of the books is necessary, and the LARP will not contain any spoilers.
King Aegon IV will be known to history as Aegon the Unworthy. On the day of his death, he legitimized all of his bastards. This might not have been a problem, if there weren't so many of them, or if they hadn't been ambitious. To complicate matters further, it appears that the previous king did not die of natural causes. No one has been accused yet, but murdering a king isn't something that ever goes unpunished.
Aegon's legitimate son has assumed the throne, but an official coronation ceremony has yet to take place. The High Septon, leader of the faith, has not blessed the new king. All of the bastards have returned to King's Landing, and have been seen in diplomatic talks with nobles from the great houses. It seems only a matter of time before one of them challenges the new king. The real question is how things will fall out afterwards.
Nobles from each of the great houses have marched down to Kings Landing. Some of them have brought their bannerman with them. It could be seen as an honor that so many men will be attending the new king's coronation -- if, of course, it couldn't also be seen as a threat.
Tonight is the night that the new king will be officially crowned as King Daeron II. There is also a great tourney being held, with his wife the declared queen of love and beauty -- a title which could be passed to another if one of his champions does not win. The new king has indicated his daughter is available for marriage, and is expected to announce an engagement. If another throne contender is to make a move, it seems it will happen soon.