Designing the Mechanics of the Big Bad

This is a reprint of a /r/DnDBehindtheScreen article published on 12 February 2016

So this sermon essay is on the combat capability of Big Bads, especially with regard to Big Bads intended for Solo boss fights. What I’ve seen time and time again are DMs and PCs coming to the fore with either a Big Bad that died within 2 rounds or a party of PCs that died within 2 rounds – the Big Bads are either too weak or too strong!For example, here.

What does one do? Raise/Lower AC? Increase HP? Make them hit harder? Softer? Personally, I typically reject these as solutions unless I intend for one or more of them to serve a specific purpose. What follows here is an explanation of the kinds of things I think of instead when designing Big Bads.

Now the common wisdom, and this is good wisdom, is to throw in a bunch of weaker monsters so that the Big Bad can afford to be “weaker” without being so quickly dispatched, and to employ challenging, difficult terrain that will hamper PC movement, marginally draining PC resources and granting the Big Bad more breathing space.

Both of these are great, but I want to add a third element: A better understanding of what has allowed a Big Bad to become, then stay, a Big Bad.

Now what makes a Big Bad big and bad to her core? Sure, there’s how powerful she is. Maybe she’s got some evil deeds beneath her belt. But IMO what separates the Big Bad from those who are just Big and those who are just Bad is…

Sensitivity to Danger

This is a lesson I learned from the Big Bads designed in the manga series Toriko.

Big Bad Boss Monsters rise not only due to how powerful or how destructive they are, but by virtue of their ability to sense and avoid danger. They need to live long enough to grow strong.

If you’re pulling out a monster from the manual and intending it to be your Big Bad, then 95% of the time you’re going to have to change its features. Most creatures aren’t built to be Big Bads. They aren’t built to last much longer than a day, or even an encounter. Big Bads have risen to the occasion through surviving that which would kill any ordinary mook. In doing so, they will have acquired techniques and abilities that enable their further survival from lessons they have learned through close calls with death.

Techniques and Abilities of the Big Bad

The following are the kinds of features a Big Bad needs to stay Big and Bad:

  • Damage mitigation. In 5e terms, either something like Evasion or Damage Resistance. If your Big Bad is lithe and agile, try granting them Evasion. If they’re big and burly, try granting them a Rage-like resistance. Personally, though, this is like the least important thing to me. If you do the rest right, you won’t need this much.
  • Mobility. However you decide to design it, Big Bads require a means to soar across the arena to prevent things like PC camping/sticking in one spot, much like any decent boss fight in a video game. The agile can have enhanced jump/fly speeds and bonus action disengages, the smart and magical can have teleports and polymorphs, and the big and burly can have stampeding charges.
  • Forced Movement Capability. Sometimes, no amount of mobility can get your Big Bad out of a tight spot. Other times, your Big Bad may have a trap set that requires the PCs to be arranged in a certain fashion. Especially if they’re a Big Bad, surely they’ve experienced situations in which they were outnumbered. So your Big Bad is likely to have strategies and techniques that apply forced movement. For the lithe and agile, try techniques that slide and drop prone; for the smart and magical, any magical forced movement under the sun (typically more powerful than but consequently not as often as any forced movement by Lithe/Agile and Big/Burly types); for the big and burly, shoves and grapple/throw. Be creative with your forced movement ability – perhaps something special to the Big Bad, a unique technique they developed – you’ll see an example later.
  • Out of Turn Effects. This is the most important one IMO. Your Big Bad needs to be more than Big and Bad – they need to effectively be multiple monsters in terms of action economy. Reactions aren’t enough. In 5e, WOTC has mechanically represented this in Legendary Actions, abilities that can be activated consuming a limited round-by-round resource at the end of any other creature’s turns. Personally, I love how 4e handled this with their “At-will Triggered Actions” (and you’ll see an example later) – Legendary Actions may suffice for this for now. Anyways, in terms of Dealing Damage, Movement, and Forcing Movement, your Big Bad needs responses to PC actions.

Try not to make any of these features impossible to interrupt! If your PCs can manage to figure out some way to interrupt an enemy’s Damage Mitigation, Mobility, Forced Movement Capability, or Out of Turn Effect, then great for them! It’ll lead the PCs away from presuming that every given boss fight is meant to be a grinding slog-fest. That you can dramatically change the game on a moment-to-moment basis without immediately ending the encounter is a great realization to behold.

Additionally, experiment with different combinations of the above features. You don’t have to include all of them in the same Big Bad. In fact, depriving a Big Bad of one of the above features could be your Big Bad’s selling weak point (though the one thing you probably shouldn’t deprive is the Out of Turn Effect one – that one’s just a bit too important).

Alternatively, consider trade-offs between these features through triggers! Like when your Big and Burly Big Bad that doesn’t normally have damage resistance hits Half Health, have him suddenly gain damage resistance and greater mobility (Stampeding Charge!) whilst simultaneously losing Out of Turn Effects or something else – perhaps his ability to differentiate from friend and foe!

And don’t forget to consider Roleplay triggers! Perhaps your Big Bad is egomaniacal, and thus has a poor sense of self-esteem. Normally he’s shrewd and calculating, but enough mean comments about his knobby knees and his hook nose might make him forget his extremely powerful and annoying Force Movement capability in favor of using a powerful, but low accuracy, attack!

More on Roleplay Triggers and more will be investigated in my next essay: Designing Goal-Oriented Encounters.


A solo boss I made early in my DMing was effectively a facsimile of the Rancor from Star Wars. His name was BOOLY.

This was for my 4e 2nd level PCs. Since this creature was Big and Dumb, I did several things: I changed his defenses around. In 5e terms, I gave him better AC and physical saving throws, while dramatically reducing his mental saving throws. After playing with his stats a bit, I added an explicit Weak Point on the top of his head.

As soon as combat was engaged, I quickly discovered that the changes I made were virtually meaningless! The PCs were still hitting him with regularity and so almost completely ignored his weak Mental aspect. Rather than investigating the red X I literally taped on to the top of his hand-made model’s head, they continued to just wail at him, and box him in. I almost immediately had to grant him a Stampeding Charge ability that would let him get out of being boxed in, at which point the fight became dramatically more fun and challenging, since now BOOLY would careen across the arena, heedless of obstacles. It was a good way for BOOLY to attempt to deal damage to multiple PCs at a time, but the saving DC was low enough that PCs could more often avoid it then not. Thus it was a constant danger, but not a devastating one. When he reached Half Health or lower, I let him immediately Stampeding Charge as a triggered action, giving him a bit of Out of Turn Capability.

It was a pretty fun fight, especially at the end when a Grappling specialized PC finally realized the significance of the head, climbed to the top, and struck point blank at the weak point, provoking me to immediately trigger another Stampeding Charge. It ended brilliantly when the grappling PC not only managed to avoid being slammed into the arena wall, but maintain his demi-godly grip as well, saving him from taking a fall.

And yet I realized something else: This was not a fulfilling Solo Boss fight! At best, it was a fulfilling mini-solo boss fight! I had intended this to be the climax of the campaign, but the PCs were just getting ready, and so I had to immediately extend the campaign for a more fulfilling ending conflict, which ended up involving a slave camp prison break, open riot, and then finally enacting a mass teleport to escape an interceding foreign army.

This was quite a crash course for me in designing solo bosses.

The best Solo Big Bad boss battle I ever conducted was from a pre-made 4e campaign called the Five Deadly Shadows. In it was a beast by the name of Yamato Sheng. He had it all: A way to remove debilitating conditions (at some cost to himself), a way to reach his targets at almost any distance (the ability to teleport after every attack he makes), a way to clear room for himself if he ever got surrounded (melee ranged aoe), a way to move and attack outside his turn (Triggered Actions), a way to force movement on his enemies, and finally abilities that triggered when a certain threshold was met (reaches half HP).

Now those of you unfamiliar with 4e, don’t be daunted by the 388 HP and defenses exceeding 20. 4e was a very different creature, and for the level that the PCs were at fighting Yamato (level 8), Yamato’s HP value and Defenses weren’t too bad.

Now what made Yamato Sheng the King of Solo Boss Fighting was his fantastic Mobility and, most significantly, his Out of Turn Effects.

Let’s briefly semi-convert Yamato’s 4e abilities to 5e terminology.

Harmony of Body and Mind is kind of like Legendary Resistance.

Reaching Steel Fist is his normal unarmed strike.

Flying Battle Step is his Multi-attack.

Spinning Leg Sweep is effectively the equivalent of a 1 time per short rest AoE power? Except that it also recharges and triggers under a certain condition (when Yamato reaches half health).

Tempest of the Four Winds is a temporary fly speed that has a 50% chance of recharging each round.

Meditation Upon Time and Space is a Bonus Action Forced Movement ability.

Redirection of Force is like a combination of a Reaction ability and Legendary Actions – it gets triggered like a reaction, but Yamato is not limited to one per round.

When fighting Yamato, he is effectively multiple monsters in a single body in terms of action economy, but not in terms of damage nor in defenses – those aspects are pretty normal. He would spend each round unarmed striking, then teleporting away from, a different PC per unarmed strike. And then he would use his phenomenal movement to fly across to the other end of the arena, forcing PCs to repeatedly consume all of their movement to just barely make it in range to attack him, and sometimes they couldn’t get in range! When they did manage to attack him, but miss, he would immediately Trigger Action attack. It’s still not too much damage, but it adds up over time! This battle went on for at least 6 rounds.

When the PCs would successfully apply a condition on to him, like Stunned or Slowed, he’d have to suffer the effect until he could as an Action end the effect through Harmony of Body and Mind, damaging himself in the meantime. Which meant several things:

He wasn’t rendered entirely useless by a successfully applied condition, but

  • he did have to suffer it for some time, and
  • he had to use his action to remove the condition rather than using his action to attack, and
  • he still took damage.

Which means while it was frustrating for the PCs to see him time and time again break free of his conditions at-will, they could consistently see the evidence for their potential winning. The conditions weren’t wasted! They cost Yamato time and resources!

You should notice that technically Yamato Sheng wasn’t alone. He was accompanied by two ongoing traps, namely Large Statues with Outstretched Arms. These statues served two purposes: 1) potentially deal a bit of damage to the PCs every now and then, and most importantly 2) discourage PCs from making bee-lines to Yamato Sheng who just flew himself across the map. Yamato gets to ignore the traps – the PCs don’t. Either the PCs expend time and resources to destroy the tarps, or they risk triggering the traps, or they avoid the traps, making it more difficult to reach Yamato Sheng. Any small mooks you throw in with your Big Bads will likely serve similar purposes.

Truly there was no Big Bad Solo Boss like Yamato Sheng!


Big Bads have unique things about them that let them be and stay Big Bads. These things are features and abilities that enable their greater survival. Big Bads don’t necessarily need greater AC, or better Saving Throws, or too much more HP. When in combat, Solo Big Bads must effectively be like multiple monsters in terms of Action Economy.


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