I’ve alluded to phased bosses a few times, but I haven’t gone in-depth about it. A phased combat encounter is any encounter with multiple stages as part of the same fight. These stages must be mechanically distinct; a knight who becomes wary of attacks of opportunity isn’t entering a new phase, but a knight who switches to a heavy weapon or descends from horseback may be. The stages must all occur in the same encounter, but they don’t necessarily have to include the same monsters or even the same battlefield. As long as you compress multiple thematically-linked fights into one combat without a significant break between them, you probably have a phased encounter.
Despite the prevalence of phased bosses in other media, D&D doesn’t have a lot of information about doing it. I think that’s because it makes the math really hard. D&D balances encounter difficulty based on Challenge Rating math or an XP budget, and phased encounters don’t interact nicely with either. If you give your players an encounter with a 200-XP phase and a 300-XP phase, it’s harder than giving them two encounters because they don’t have the rest in between, but it’s easier than one 500-XP encounter because they’re not dealing with it all at once. D&D doesn’t like taking carefully-crafted mechanisms and adding a rule that says “and then you just wing it, we guess”, so there’s little literature on phased encounters. And that’s a shame, because good phased fights are among the most flavorful, exciting, and interesting fights you can give your players.
My first interaction with phased bosses in D&D was during Delve Night, our FLGS’s accidental attempt to blow 4E wide open. We had several sessions that explored strange mechanics or created new ones entirely, and I could regale you with all sorts of stories about our successful and unsuccessful sessions. One thing we noticed was that players were able to withstand numerically impossible encounters as long as they were spread out appropriately. This trend is a surprise to absolutely nobody; a 4th-level party probably cannot beat four CR 6 monsters at once, but if you spread it out over several fights it’s merely somewhat difficult. The game’s entire balance is based on splitting challenges into manageable pieces.
What we hadn’t predicted was the severity of this trend. When we started with phased battles, we doubled our XP budget. That is, if we knew a typical party could handle 1500 XP of enemies, it meant our Delve Night players (who only fought one battle per session and benefitted from the dreaded “ten-minute adventuring day”) could handle about 3000 XP of enemies. Our theory was that the group could basically fight a fair encounter, then immediately fight another fair encounter with little or no downtime. Yes, they hadn’t regained any expended encounter powers, but anything with a duration of “until the end of the encounter” was still in effect, and that came close to evening out. The PCs still succeeded, so we pushed a little harder to see where the limits were. We found it wasn’t unreasonable for the party to win against an encounter with an XP budget three times the recommended level, and it was possible to go beyond that based on the rolls, the characters, and the time we had in the session.
This was a specific circumstance in a specific campaign; I am absolutely not saying “phased battles will let you hit players with triple the normal challenge”. The point is that dividing battles into phases lets you hit the players with more than you might think is fair, even taking into account the phased nature of the combat. There are a few reasons for that:
Limited actions. Remember the recent post where I recommended having encounters with multiple monsters because that gives you more actions to affect the players? Phased battles do exactly the opposite. If the players fight three town guards, all three of those guards get an action every round. If the players fight one guard and then fight two more once the first falls, those two guards don’t affect the combat until they join it. The players aren’t fielding attacks from them, or using spells to control them, or taking their positions into account as they move into flanking. Because their ability to affect the battle is limited, they don’t count toward the encounter difficulty the same way.
Increased buff relevance. Buff spells that last for a few minutes usually run the length of a combat, but not two. There’s rarely enough time to stop and rest between fights while keeping on such a short clock. In 5E, where buffs are often concentration spells and a short rest takes an hour, it’s usually outright impossible. A phased encounter compresses more combat into a smaller time frame, and buffs from the first phase tend to remain in effect when the second phase begins. Spells that last for five minutes are more appealing when a player knows they’ll have more to do within those five minutes, especially when they consider the cost of casting that spell instead of attacking. With more incentive to buff themselves, the players make themselves stronger than they would be for a normal encounter, which means they can handle more danger than usual. Even if your party isn’t big on buffing (or you’re playing 5E, which doesn’t like it very much) the same principle applies to lingering battlefield effects, like entangle or grease, that let the party set something up and reap the benefits throughout the fight.
Multiple pluses. Phased fights are rarely multiple instances of the same challenge. Even in the above “one guard / two guards” example, where the monsters are the same in both phases, the number of enemies makes the second phase different. For example, the first phase benefits a fighter who excels in locking down a single enemy and the second phase benefits a wizard who prepares multi-target spells. Phases give you an opportunity to define multiple pluses in a single encounter. This gives different players a chance to shine in different phases, which means the party has more opportunities to use their biggest guns and control the pace of the fight.
Recovery options. The nature of a phased fight gives you the option of letting the players rally between phases. In a normal fight, it doesn’t make sense for a character to suddenly spend a Hit Die or recharge a spent ability at a random time. But you can have a sort of partial rest between phases, where characters gain some benefits of a rest without actually taking it. You’re rewarding the players for reaching a milestone and giving them a bit of heroic recovery, but not going so far as letting them take an actual break. This lets the players expend more resources than they should have, and sometimes it makes up for bad rolls or decisions by letting players regain whatever resource they need the most.
Of course, focusing on the difficulty implications of phased encounters avoids the best reason to use them: they’re fun. A phased encounter is, by definition, bigger than a normal fight. It’s longer, it’s tougher, and it can fit more monsters and challenges. It has built-in dynamic elements and phase transitions that give players specific, measurable progress toward victory. It lets you break the normal rules for how strong a villain should be but doesn’t ignore the game balance to do it. And beyond its mechanical qualities, it also brings to mind any number of fights in video games or comic books or television shows where the villains respond to an imminent loss by escalating instead of giving in. A phased boss is, in a way, an ideal boss, and it’s a travesty that the rules have no place for it.
But charismatic DMing involves a healthy disrespect for rules as written, especially when they get in the way of a good time. In the next post, we’ll talk about the types of phased bosses and get into some actual numbers.