Dragon Encounters

Making dnd combat fun, finding monsters that fit together, monster tactics and strategies, and other ways of using the monsters of dungeons and dragons

ANCIENT BLUE DRAGON: The Ultimate Boss Dragon



Combat rating 26


1 Ancient blue dragon (CR 23)

2 Ultroloths (CR 16)


Combat rating 27 (65-37.5=27.5)


1 Ancient blue dragon (CR 23)

1 Death knight (CR 23)

5 Revenants (CR 23)

1 Young black dragon [optional] (death knight’s steed)


Combat rating 28 (72.5-37.5=35)


1 Ancient blue dragon (CR 23)

2 Air elementals (CR 23)

2 Earth elementals (CR 23)

2 Dao (CR 23)

1 Purple worm (CR 23)


Combat rating 29 80-37.5=42.5)


1 Ancient blue dragon (CR 23)

3 Clay golems (CR 23)


1 Stone golem (CR 23)

2 Shield guardians (CR 23)

1 Gynospinx (CR 23)

How to Use

The ancient blue dragon maintains a tight watch over its territories, and the PCs should not be able to approach it (except magically) without it knowing about it well beforehand. (For that matter, it should really take some steps to prevent anyone being able to just teleport in. If you don’t want to have an anti-teleport spell over the area, perhaps it keeps the location of its lair secret, so they don’t know where to teleport.)

Well before they reach its lair, they should already have to fight off multiple attacks by the dragon’s minions. More than stopping them, the objective is to learn what it can about their abilities. In addition, to cause them to waste their strength.

The dragon will not let them have the time to take a long-rest. Neither will it let them retreat. It will wait to have its minions launch their first attack until the PCs are sufficiently deep into its lands that they can’t easily retreat. Then, it will poison springs, take down bridges, and have its minions make hit-and-run attacks in order to bleed away their strength.

(In a D&D game, where you need it to be fun for the players, prepare several interesting challenges to go along with the above strategy, if using. Give evidence that the spring might be poisoned, such as a dead monster near it, and let them decide what to do. Wait until they’ve in the middle of crossing the gorge without a bridge, and then attack them when they’re out of position. Describe the heat, ask them what they do, and give them a level of exhaustion if they didn’t seek shelter, or roll boulders down onto them if they sought shelter in the caves. Plan interesting harrying attacks, don’t just use random encounter type tables.)

Combat Encounter – Canyon (Difficulty 18)

Once it’s ready to start up with them, one of the moves it might do would be to chase them through a narrow canyon. The dragon will be at the top, and it will use its attack actions to bring down the cliffs up above on them in an avalanche of falling stone and dust. Using chase-like rules, the players will have to keep ahead of the devastation, or they’ll take a lot of damage from falling boulders and be blinded from the falling dust. (Similar to its lair action.)

To keep the players from knowing what’s going on, narrate it as though the dragon’s entire objective is to hit them with the rubble. Let them make saving checks, and let them use illusions, overhangs, and/or anything else they think of to stay ahead, rewarding them by having the rubble fall behind them, without them having to make saving throws.

In addition, have the canyon be full of sharp corners, so they can’t see far ahead, and let them know that the end of the canyon isn’t far. (Maps, or being able to see that the canyon walls are getting smaller.)

If any PCs try to climb/fly/teleport up, have the dragon use its lightning breath to send them back down. If there are more tries, and its breath is on recharge, it can also use its wing attacks, its fear presence, and physical attacks to knock them back down. Remember, even if it uses its action to know them down, it has its legendary actions to help bring down the cliff.

After a round or two, have them come to an obstacle which they’re going to have to cross, and in a hurry. Different possibilities include:

  • A long, deep chasm. There was a bridge over, once, but that bridge was taken out.
  • A wall, cutting them off. There are rows of spikes on the far side, which means that once they’re up, they can’t just jump down.
  • A series of concealed pits. Given time, they would be easy to discover, but time is what they don’t have.

The end of this chase, and its main purpose, is when they come out of the canyon straight into an ambush. I somewhat fancy 2-3 purple worms, with the noise of the canyon collapsing guaranteeing that they’ll be woken from their slumber, but you could also use regular minions. Perhaps archers and mages, surrounding them from multiple sides, safe behind barriers to give them cover. Add some pits or spikes to make it hard to reach them. (There will probably be at least some melee, as well, but they’ll stay behind the barriers until the PCs reach said barriers. Their job is to protect the archers/mages, so they’ll wait until they’re needed.)

The dragon might involve himself in the combat, but I would restrict his involvement to strafing the PCs with his breath weapon when it’s available. This battle isn’t necessarily to finish the PCs off, although the dragon will be happy if that happens. This is to weaken them, and to discover more about their abilities.

I will remind you again that the dragon should not give them time to rest, and that goes double here. After this fight, the dragon should try to keep them on their toes, sending minions at them constantly. It doesn’t matter whether the minions have a chance to win, it just matters that the PCs don’t have a chance to rest. If they try to retreat, it’s even more important to make certain that they don’t manage it. If they do, they’ll come back, and be more prepared when they do.

(Speaking more directly to the DM: You have to balance what your players can handle, but if you give your players to much leeway, they’ll very possibly annihilate the dragon. High level PCs are incredibly powerful. In addition, you can’t really reuse this or the following encounters to any real effect. The players know that they’re there. I would consider very carefully before sending them against this dragon, in particular, and try to make it all or nothing once you commit.)

The Dragon’s Lair

(Note: I already made several suggestions regarding the adult. Those would work fine here, but I’m giving some new ones as benefits an ancient dragon.)

1. The dragon’s lair is high up on a cliff face. Any stairs leading up were either destroyed as the PCs approached, were booby trapped by having their supports weakened or removed so that if someone steps on them, they’ll give way underfoot, or have multiple murder holes all along their length.

(Murder holes is a medieval defense. It means small holes through which boiling oil or other unpleasant things can be dumped down onto the invaders. In D&D, acid, poisons, exploding rocks [see Magic Stone cantrip] can all take the place of burning oil. So can tiny projectile weapons, such as [possibly poisoned] darts. Using murder holes assumes that the dragon has minions with access to its lair.)

There is a balcony jutting out from the entrance to the dragon’s cave, and this is where the dragon will first engage them in directly. Unknown to the players, the balcony is rigged to fall when triggered.

There are two ways this can be run. The first is to have a weak point in the bottom of the balcony. If you do this, I would put 2-3 monsters guarding the entrance (golems would do nicely. So would other constructs.) The dragon will attack from behind, using the superior reach of its attacks to hit and retreat without taking attacks of opportunity. After 2-3 rounds, before the players have a chance to completely finish off its minions, the dragon will dive and target the weak point with its breath weapon, causing the balcony to collapse.

The other way is to have a lightning rod sticking up from some part of the balcony. The rod goes deep into the balcony, and connects to multiple support beams and/or ropes embedded in the balcony. The support beams have been made deliberately weak where they connect to the rod. When the dragon’s breath hits the rod, the lightning energy will course through it and sever these connections, leaving the balcony about to collapse.

If you want, you can make the area below the balcony be a covered pit. The pit was covered with a strong covering, allowing the PCs to walk on it without even realizing, but the weight of the balcony falling on it will crack the cover, and send the PCs all the way down to the bottom of the pit. Add sharp stakes at the bottom.

If the PCs end up avoiding the fall, and manage to get into the lair before the dragon, you’ll send them into a long tunnel, or you’ll make them move a heavy boulder out of the way while the dragon tunnels in from the side. Blue dragons can burrow, and you can say that the dragon kept a place or two where the rock face was only 5-10 feet thick, just in case it needed an emergency entrance/exit.

2. Exploding Barrels: A deadly setup for the inside of the lair comes in the form of barrels of explosives that the dragon placed in a few strategic areas around its lair.

An ancient blue dragon’s lair will be a maze of large tunnels and larger caverns, through which it can fight and run, defending any given area while it’s tactically advantageous and retreating as soon as that’s the smart thing to do. One thing it will do to make fighting in a nightmare is exploding barrels.

Exploding barrels are any barrel packed with an explosive substance. If explosives are too modern for your tastes, flour packed tightly and heated up without room to expand also explodes. If even that is too modern, use barrels of oil. Unlike the first two, this won’t explode, but it will burn, turning the cavern into a fiery inferno. While the dragon isn’t immune to fire damage, it will watch where and when it sets it off, and try to keep the PCs inside the burning cavern while it fights from outside the flames.

Both explosives and fire will do damage. Explosives will destroy terrain around the area, bring down the ceiling on them to trap them, and perhaps fling them sideways and/or prone. Fire will set up an area which will do damage every round they stay in it.

Even if you are using explosives, you might want use some barrels of oil also for variety. Or, you could pack both into the same barrel [or adjacent barrels] in order to have an explosion the also lights the area on fire.

The barrel will be placed in the center of the cavern, opposite the tunnel down which the dragon is located. The dragon will fight to defend the exit, placing itself far enough down the tunnel that ranged attackers and spellcasters need to enter the cavern in order to have line of sight on the dragon. Then the dragon can use its breath weapon to target the barrel, and hopefully catch several PCs in its line of fire as well.

(Even without the barrel, staying at the back of a tunnel isn’t a bad position for the dragon. While the size of the dragon means that the tunnel won’t be narrow enough to certainly catch multiple PCs in its line, it raises the chances.)

Another way to use barrels is by sending a barrel rolling down toward the PCs like a boulder trap. Barrels are heavy, and should do quite a bit of damage if one crashes into the PCs. If they smash it with a spell, they might set it off themselves.

If the players get the barrel to a spot where the dragon’s breath can’t hit it, or if the dragon’s breath didn’t recharge as soon as you hoped, you can also use the lightning lair action to set it off. Be aware that while the explosives will go off the same way, the flour will probably make a smaller explosion, and the oil won’t scatter as widely, given the smaller damage of the lair action as compared to the dragon’s breath weapon lightning. 

In order to get the barrel rolling without wasting a full action, have it be tied to a rope or column which the dragon can destroy with a single attack, or legendary action (tail option). Alternatively, have minions send it rolling, or have the PCs set it rolling when they step on a hidden lever. With either of these last two options, you can have the barrel come from behind or from the side.

3: Collapsing Floor. In the adult blue dragon article, I suggested that you could have the ceiling be loose earth lightly covered and held up by stone or glass, so that when the dragon activated its lair action to collapse a part of the ceiling, the entire ceiling starts coming down. You can do a similar thing with the floor.

Have the floor be a sheet of glass. The players won’t necessarily realize how thin it is, as it can easily be covered with dirt/sand. As the ground below it holds it up, it won’t give way straight away. When the dragon triggers its collapsing ceiling lair action, that might break the glass, if it isn’t buried too deeply. A boulder trap will likely break the glass. The dragon’s breath weapon should break the glass, although you should have it send its lightning near the floor (this won’t affect how many PCs it hits.)

The barrels from the last idea will definitely break the floor when they explode, and the dragon might be able to break the glass by stepping on it, depending on how fragile you want the glass to be.

(If the glass won’t hold up to the dragon’s weight, then this room is one that the dragon keeps to use against invaders. It might have a series of pillars sticking up from the room below, their tops level with the glass, that it uses as stepping stones. [Although the dragon’s minions might use the chamber.] Personally, though, I prefer to have the floor be strong enough to hold the dragon’s weight, and have it be broken by the barrels or breath weapon. It’s up to you.)

Once the floor breaks, the loose earth/sand underneath will act like a sinkhole, drawing PCs down and leaving them trapped. (I discussed sinkholes more at length in my last article.) If the glass wasn’t buried, any PCs not wearing heavy armor might take some amount of damage from the broken glass, and more if they get knocked prone.

Once part of the glass is broken, the rest will give away much more easily. Even someone wearing heavy armor and getting knocked prone might do it.

One more detail. If the loose earth/sand is held in place by glass from the side, or one of the sides, and that side is somehow broken, the loose earth/sand will start draining out and the glass will no longer be able to hold the weight of anyone on it. You could use this as a feature of the trap, or as a different trap idea.

Similarly, if there is loose earth/sand behind a glass wall in a cavern without this special floor, and the glass gets broken, possibly be the dragon’s breath weapon, the earth/sand will start pouring out. Some PCs might get covered/trapped, or the earth/sand might end up pushing away PCs in its path, possibly pushing them into a chasm or the like.

4: Snakes and scorpions. In many of the ideas mentioned previously, in this article and/or the last one, the players get covered in sand and or sink into sand. If you place a number of poisonous snakes and/or scorpions mixed into the sand, the experience will obviously become a lot deadlier.

You could also have a cauldron or other large basin of sand that the players trigger, as a trap, and have it dump earth/sand with snakes/scorpions down onto them. While the sand might seem unnecessary in this case, it will make it harder for a Fireball or similar spell to target all the snakes/scorpions, and it will also distribute it more widely. Finally, it might confuse the players into not realizing right away that the sand/earth is full of snakes/scorpions.

Bonus: Cavern obstacles. Some things you can do to differentiate caverns in the dragon’s lair:

  • Chasms running along the floor, some from side to side and some from front to back. The front to back ones will force the players to either move in single file or to split the party up to its two sides.
  • Large stones, or other means to reduce movement. You will need to leave a large space for the dragon to move, or you could have the obstacles be statues and the like that the dragon knocked down to use as obstacles. The dragon has the reach to attack past obstacles, so you can use them as barriers which the dragon reaches over or you can use them to protect the dragon’s sides.
  • Different heights: Have the players enter a cavern where half the floor is 10-feet above the other half. The dragon can be on the higher half, in which case it will have the reach to hit PCs below, and the PCs won’t have the reach to hit the dragon. Even ranged might have trouble getting a good line of sight. Or, have the PCs up high, and the dragon can move in and out of range to attack. You can also split up the heights along the cavern in a side-to-side manner, or other ways, to create obstacles and variation.
  • Loose sand floor, and a slope. Not having a strong place to step will make going up much harder, descending might require a DEX save to avoid sliding more than was meant, and perhaps incurring an attack of opportunity. And of course, when combined with chasms it goes from a nuisance to deadly.

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About Me

I have been a DM for several years, and I was designing home RPG games since my young childhood. I have been a fan of many different types of games (computer, board, RPG, and more) and have designed several for my own entertainment. This is my first attempt to produce game content for a wider audience.