I don't know exactly how this came up, but this is an idea that has never really occurred to me. You see, I have a problem. My games never feature reoccurring villains. The reason for this are simple- most of the time, when I tell my players that someone is a bad guy, they try and kill them. And since D&D is stacked in the favor of the players, most of the time, they succeed. But today, I came up with an innovative (for me) idea. If I can't make my villains stick around, I might as well make their deaths memorable.
So, here's how you do it.
But first, a note. This isn't a system that's meant to apply to just anyone, it should only apply to named antagonists, big bads who are squatting at the center of an adventure, interacting through intermediaries, leaving scurious notes for the players in the remains of his latest crime. A Dragon who happens to be sleeping at the bottom of a dungeon should not get this treatment just because he's a Dragon. However, he should get this treatment if he has been burning the countryside and stealing handsome shepherdess, and the whole adventure has been about stopping him.
Step 1: Defenses - Actually reaching the monster
Most monsters have a way to prevent you from actually damaging them. They have 1d6 layers of extra protection around them. This can be a force field, tentacles or long appendages that surround and make nuisance attacks, telekinesis which throws people back, etc. Regardless of what they are, the rule is this: there must be a way to disrupt or break through these defenses. Usually the option will be physical force, ie the Dragon's armor begins cracking after enough attacks. But if physical force is not sufficient to shatter these defenses, then other options must be discussed and offered to the players, before the final confrontation with the Boss Monster. The players should be prepared for their fight with the Boss.
Step 2: Pesky Damage Reduction
Secondly, all Boss Monsters have some kind of resistance to normal damage, for whatever reason. Whether they are enormously tough, or too big to actually hurt with conventional small arms, or magically protected or etc, this is what you rely on. Even if you pierce their defenses, most of your attacks aren't going to hurt them much. But they should still take damage.
Step 3: Where do I attack - or how I learned to stop worrying and love weak points
Now, that damage reduction I mentioned above has two purposes. Firstly, it keeps your Boss living for a few more rounds. But secondly, it opens up the concept of player teamwork to reach a Boss' weakspot. All Bosses have multiple weakspots, some obvious, some not. For example, the ring on his left ring finger is a power amplifier, or the pulsating eye on his back, or his open, unarmored mouth, etc. A weakpoint can also be more abstract, but regardless of what they are, make sure they have two things.
Firstly, weak points must be obvious. If at all possible, tell the players about them explicitly, unless they figure them out before you can.
Secondly, weak points are where damage reduction does not apply.
Step 4: Wind-up attacks aka how to telegraph your killing intent
A quick digression: How I, and I imagine most people run combat in a narrative sense is like this. First, I address the player and quickly remind them of what is happening. Then once they answer, I explain what happened, and move onto the next person. I imagine this is the way all competent DMs do it. But the way I do it is slightly different. The Angry GM, a veritable genius you've probably heard of, is the one who came up with this system, and he explains it far better than I here.
But to make a long story short, read this:
"DM: Okay, Bob, A Goblin is pouncing on Alice, dagger raised to drive it down into her stomach. Behind you, Robbins is fighting off the other two with wide swings from his mace. What do you do?
Bob: I cast Magic Missile!
DM: Roll then.
*Bob rolls dice*
DM: The spell flies from your finger tips, striking the Goblin on top of Alice. The tiny dart distracts it, turning its *rolls d20* attack into a near miss, allowing Alice to shove it away. Alice, it's your turn. The Goblin that was just on top of you is scampering off the ground, ready for round 2..."
That's essentially how I do it. If you're doing it properly, combat flows smoothly, like a dolphin diving in and out of the water.
And that works fine for little monsters, who only do 1d6 damage. But Bosses are different. I want Bosses to have big, room-wiping, party devastating attacks that do huge amounts of damage. So, this is what a Wind-Up attack is.
They work just like a usual attack, but instead of starting on the Boss' turn, it starts on someone else's turn, with the attack actually going forward on the Boss' turn, as per normal. Here's an example:
DM: The Great Wyrm snarls down at you, his golden blood dripping from a dozen petty wounds. "I will enjoy watching you die, Mageling!" Smoke begins pouring from the Wyrm's mouth, and it turns its muzzle toward you. This is the fire breath that melted the king's crown like a candle melting cheese. What do you do?Or...
Bob: I cast 'Fire Shield', then run like hell!
DM: Just in time, for as the Wyrm breathes, sunfire spews from its maw, engulfing you and the whole field. Around you, the long grass explodes into plumes of flame, instantly surrounding you in a burning labyrinth. Lucky for you you cast that spell, otherwise it would have melted you!
DM: The Great Wyrm snarls down at you, his golden blood dripping from a dozen petty wounds. "I will enjoy watching you die, Mageling!" Smoke begins pouring from the Wyrm's mouth, and it turns its muzzle toward you. This is the fire breath that melted the king's crown like a candle melting cheese. What do you do?
Bob: I'm going to try and kill it.
Alice: No, just run! If you roll low enough on your Disintegrate spell, who knows what will happen?
DM: She's right you, know. You miss, and you'll be nothing but ash.
Bob: Screw it, I'm going for it. I cast 'Disintegrate', targeting the Dragon!
*Bob rolls dice*
Bob: Oh. Shit.
DM: Unfortunately, you miss, the vermillion beam flying from your fingertip, only for the Wyrm to duck, and the beam soaring overhead to strike the rocky ceiling. The Wyrm seems to smile at this, before unleashing its sunfire breath. You take *rolls dice* 21 damage. Can I get a saving throw?
Bob: It won't do any good. I only had three HP left.
DM: Oh. Well, Alice, Robbins, you just saw Bob get disintegrated, his body instantly burnt to ash by the Great Wyrm. What do you do?
This is the best solution, I find. It gives Bosses the ability to do large amounts of damage, while also giving the players the ability to take evasive action or deploy countermeasures in the face of the attack.
Additionally, as one final countermeasure, until the Bosses activate their Rage of the Gods mode- they can only make one Wind-Up attack a round, and must wait for the Initiative order to reset before making another one.
Step 5: Multiple Moves- Breaking the Action Economy
The Problem of the Action Economy is the thing that always brings down solo monsters. The PCs can make 3 to 5 actions, the Boss can only make one. This is an obvious disadvantage for the Boss. The usual solution to this problem is to boost the Boss' HP by 3 to 5 times, and make their one attack do 5 times as much damage. But I already have Wind-Up attacks for that. So instead, here's a simple fix.
Bosses get multiple actions. Most larger monsters get multiple attacks, such as multiple claw attacks or bites. So for a Boss, have them roll initiative multiple times and divided their attacks among those turns. Since most large monsters usually have two weaker attacks then one stronger one, ex: Claw 1d6/1d6 + Bite 1d12, put two of the weaker ones together and the stronger one by itself. That way, instead of an Order looking like "Fighter, Boss, Wizard, Thief, Cleric" it looks like "Boss, Fighter, Thief, Wizard, Boss, Cleric, Boss".
Step 6: Rage of the Gods- the Home Stretch
So, finally, after the Boss' defenses have been removed, the Weak Points targeted, now we enter the final stretch. This is the final part of the fight, where things get dangerous. This part doesn't need a lot of explaining, when a Boss' health is depleted, they get access to a second pool of HD, and they get more dangerous as well. This is when the Boss transforms into their giant, city-destroying form, or they finally access their full potential, or etc. However, I would advise not giving them any new powers during this form, as the players might feel cheated by that.
Gorranus, the Great Wyrm
1) His thick scales are near impervious to any weapon not specifically crafted to fight a creature of his pussiance. He can use his armored flanks and arms to parry blows, reducing the damage taken. You break through this defense by moving around it, to his more vulnerable belly or other soft spots.
2) His wings also work like shields, not only enabling flight but allowing him to disregard ranged attacks entirely, as they superheat the air beneath them, allowing him to melt any projectile that flys near them, and slowly broil anyone unlucky enough to be caught beneath them. You break through this defense by cutting through his wings. They do not have the Damage Reduction of the rest of his body.
Damage Reduction: -3 to all attacks on his body, and -5 to all attacks on his arms and flanks, as per defenses. His wings have no Damage Reduction, but they also have separate HD from his body, and while damaging them hurts him, it does not impede his fighting ability.
1) His stomach. If you can get underneath his body, you will find it much softer.
2) His eyes. If you stab them out, you will also blind him.
Sunfire breath: Does 2d12 damage, and can raise the temperature of stone to the point where it burns flesh on contact. Also heats metal to the point where they glow red hot, and causes all unprotected flesh or burnable material to combust.
Gorranus acts three times in a round, not counting his Wind-Up attack. He acts twice in the Initiative order based on his 1d20 rolls, rolling separately for each, and then once after everyone else has taken their action.
Rage of the Gods:
Gorranus can make 2 Sunfire Breath Attacks per round.
Alcyone, the Thunder Wizard
Protected by the Wind: All projectiles against them miss, and all melee opponents are flung backwards with hurricane force. This cannot protect him from something that the Wind couldn't, like say, a flung boulder or a hellfire missile.
Cloud Armor: Alcyone can partially transform himself into clouds to escape from danger. He must keep at least part of himself solid when he does this.
Wall of Wind: Alcyone can make walls of wind across a space, that push anything outside the wall away from it, while not moving on the outside. Also, this tends to suck the air out of a place, but in any area with decent ventilation its not a problem.
His body that can change from cloud to flesh and back in an instant means he can ignore damage from non-magical sources while in cloud form, and when he returns to flesh form, all damage done to him will be undone.
1) His ring of Wind Wall. Cut it off his finger (or steal it in some other way) and he will be unable to make walls of wind.
2) Alcyone is protected by the Wind, but it is a jealous lover. If he were to ever wear armor, that protection would vanish.
3) Alcyone's cloudy body can change shape, but any magical weapon could hurt him, even in cloud form.
4) The winds require open skies. If Alcyone were ever forced into a confined space, such as a building, or even better, underground, he would find his abilities significantly weakened.
Wrath of Heaven- Lightning bolts pour down from the sky, and strike one person. Does 1d20 damage, save for half. But it is lightning, and will strike metal or tall objects before they will strike a person.
Alcyone acts two times in a round, not counting his Wind-Up attack. He acts once at the start of any combat and then acts once in the Initiative order based on his 1d20 roll.
Rage of the Gods:
Alcyone transforms into a living Thundercloud. He can make his normal attacks from this form, is immune to all non-magic damage, and can use himself to cast Wrath of Heaven, even if he is below ground.
Razor, The Russian Psychic
The Black King