At any rate, The Boss Fight was originally intended to fix dragons and, as I’ve said, I lost control and devoted more time to the system than the actual monsters. The first example of what I was trying to do was not even a dragon.
But I am here to make up for it with my entry into Colmarr’s Monster Mayhem Blog Carnival and, in so doing, codify the final Boss Fight system.
The Core Boss Fight System
A Boss is a special type of Solo monster. Mechanically, it has the same hit points, defenses, attacks, damage, and save bonuses as any other Solo Monster, there are a few key differences. The biggest difference is that the Boss Monster consists of three separate stat blocks, called Stages, that it proceeds through as the fight progresses. All three Stages must be defeated or overcome as part of a single encounter and the total encounter is worth as much XP as a normal Solo Monster.
Each stage of the Boss Monster has exactly one third of the hit points of a normal Solo Monster and has no bloodied state. Each stage also includes a triggered action that is triggered when that Stage is reduced to 0 or fewer HP. That action causes the Boss Monster to perform some final action that usually results in it disengaging with the party and ultimately causes the Stage to be removed from the battle completely and replaced with the next Stage as if a new monster had entered the fight. The new Stage rolls initiative and acts normally. This action is called a Stage Transition.
The Stage Transition never requires an action (it’s ‘no action’) and it always includes language that indicates that it is usable regardless of what is happening. It will also specifically note that the old creature is removed from the battle and replaced by an entirely new creature so that nothing carries over from one Stage to the next. This is done to trump and/or prevent any odd rules interactions that might come. Nothing carries over from one Stage to the next; each Stage is completely modular.
The third Stage of a Boss Monster is always its Bloodied Stage. This allows the party to use abilities that key off of a bloodied monster. Thus, each Boss Monster in Stage 3 has a trait that indicates that is always considered bloodied.
Each Stage of the Boss Monster has one action point.
These are pretty much the core rules of the Boss Monster. In order to qualify as a Boss Monster under my system, those are the core rules. Everything else is really just window dressing.