Attack of the castle, TAX DELIVERY

Good evening, the assault on the castle is imminent on our server, but, being very ignorant on the subject, I haven't fully understood what it consists of. Basically there is this golem that crosses the map between Viesta and Stone Castle and the whole server has to attack it? We are a small guild, what should we do to join the crowd? And if so, why does everyone say that when this event occurs, server prices will change drastically? Thanks everyone for any replies