Creating monsters for 5th edition D&D can sometimes seem like an arcane art. You only need to check out pages 273-283 of the Dungeon Master’s Guide to see the extent to which creating a foe and determining it’s Challenge Rating (CR) can become a strange kind of theoretical maths. I’m here to tell you that it’s not all that hard. It can be as easy as taking an existing monster, and swapping out some damage types and flavour. It can however become slightly more complex for high CR creatures (20+), so here I’m going to delve into the design a little.For low CRs, it really can be a simple swap and chop job. In my adventure The Theocracy, I turned the hell hound (Monster Manual p182) into a holy hound by swapping out it’s fire breath for radiant breath, and giving it a pair of wings (fly speed of 30 feet). Those simple, subtle changes are enough to completely change the theme of a monster. The same thing has been done countless times by other creators and designers, a recent example of a simple addition to an existing monster (plus a few other simple changes) is the blazing skeleton from Mike Mearls’ Happy Fun Hour.
At higher CRs, there can be a little more to consider, especially if you’re trying to create a legendary monster like an ancient dragon sorcerer, or a demon lord. In my opinion, you should focus on three core aspects; Danger, Defence & Distinctiveness.
Obviously, a legendary monster has to be able to kill characters and other monsters. They should be terrifying, anxiety-inducing terrors capable of deterring the most seasoned characters and the most foolhardy players. In order to make a monster dangerous, you need to consider the following.Number of Attacks. High CR monsters need to be making lots of attacks. If you’re one boss monster is supposed to fend off a party of high level characters, it needs to be at least matching their attacks. For a party of four, that could be upwards of eight attacks! In order to make this happen, it’s necessary for high CR monsters to have Multiattack, and typically one or more attack options in their Legendary Actions. An alternative to this would be some kind of spellcasting, or the ability to hit multiple creatures with one attack. A fireball or similar attack should hit at least two foes, if not more, and thus can be thought of as two attacks. In my opinion, a monster with a CR of 20+ should be making five attacks a round, including those it gets from Legendary Actions. This ensures it can threaten players frequently.
Kind of Attacks. As mentioned above, attacks that target only one character are the staple attack of monsters, but don’t rule out spells or abilities that can have several targets. The majority of high CR creatures have some form of multi-target attack, such as a dragon breath weapon, or Jubilex’s eject slime attack. Don’t make the mistake of neglecting ranged attacks either! High level parties fly around the place like you wouldn’t believe, and you need to snipe those suckers! If a ranged weapon attack doesn’t seem to fit, you can always use cantrips like firebolt or acid splash, which are generic enough to fit almost anything. On a similar note, a large quantity of CR 20+ creatures have the Magic Weapons trait, which helps them overcome pesky resistances.Attack Bonus and Damage. Without getting into the nitty gritty of it, a CR 20+ creature needs to have a high attack bonus, and a high damage output. One or the other won’t do, you need both. Typically they should have at least +10 to hit, probably slightly more than, and they should be dealing upwards of 100 damage split across their attacks. Remember that your monster could be making around 5 attacks, so each attack need only do 20 points of damage each. Around a quarter to a third of this will come from your damage modifier. One potent way to damage characters are aura effects which don’t require rolling to hit, or saving throws. A good example is the balor’s fire aura, which deals 10 damage to creatures within 5 feet of it, or that hit it with melee attacks (and they’re only CR 19), nasty!Other Abilities. Some of the most interesting dangers a monster may present aren’t just the numbers game of attacks and damage, but the more mental stuff that wacky abilities and well-chosen spells can create. A fireball is always useful, but a dominate person or create undead is more likely to cultivate a fun combat scenario. Abilities that cause fear, charm targets, or introduce terrain effects to the battlefield allow the combat to evolve beyond just a maths problem, and into a cinematic battle scene. Be wary of abilities that take players out of the fight though. Banishment is a great spell, and can sometimes cause huge tension in combat, but a player stuck in a prison demi-plane might end up checking their phone at the table more than one going head to head with a pit fiend.
Even if your monster can kill with a single hit, and turn an entire village into an ashen wasteland with a flick of the wrist, they can’t really be considered legendary if they can be killed by an angry dog.Durability. The most obvious way to measure a monsters defensive capability is in the form of hit points and armo[u]r class. Most CR 20+ monsters have at least 300-400 hit points, and typically have ACs between 18 and 22. If you think about your high level party, each character probably has the potential to deal 100 points of damage a round, and is likely to hit an AC of 20 about half the time. Although you don’t want a fight to drag on for round after round, you do want your monster to be able to show off it’s abilities before going down, and also last long enough to make the combat seem like a genuine struggle.
Manoeuvrability. One of THE most important defensive features of a monster is its manoeuvrability. A large number all CR 20+ creatures can fly or teleport, both of which help to keep them out of range of people with big arms swinging big swords. This can come from natural/magical abilities, such as having wings, or from spells like fly and misty step. Lots of high CR monsters also have the ability to move as a Legendary Action, sometimes without provoking opportunity attacks. This ability to dance across the battlefield means that your BBEG isn’t likely to get pinned down and whaled on by the characters. You should also consider this when thinking about getting away. BBEG’s often make repeat appearances, taunting the characters when they’re at their lowest, or escaping from combat at the last minute to appear in future adventures. This is often achieved through spells such as plane shift or teleport.Resist-ability. As well as the above measures to avoid being incinerated, a CR 20+ monsters needs fail safes. We’re talking proficiency in at least 3 saving throws, if not more. We’re talking legendary resistance, 3/day is the average and optimum (just enough times to get the characters counting, but not so many that they feel useless). We’re talking magic resistance for a further bonus against save-or-suck spells. The above are the obvious measures you can take to resist the kind of spells that turn you to stone, or take over your mind. Other things that help you resist the will of the players are abilities that cause negative conditions like fear, stunned, poison or paralysed. Poisoned is one that a lot of monsters have. A poisoned creature has disadvantage on attack rolls and ability checks, which means you (the monster) are far less likely to get hit. The final essential are damage resistances and immunities. These should be thematic based on the specific monster, but should almost always include at least resistance to bludgeoning, piercing and slashing damage from non-magical attacks.
Special Mention – Senses
Don’t forget that a creature is at its most vulnerable when it is incapable of perceiving its surroundings. CR 20+ creatures ought to have high Passive Perception scores to help avoid assassination, as well as potent darkvision, or even truesight allowing them to keep invisible creatures at bay. The same works in reverse for offensive tactics. If your monster can turn invisible, or create darkness from which to strike, it’ll make it a formidable foe.
Alright, you got me, I was going to call this something like character or uniqueness, but I wanted 3 D’s. Numbers aside, what makes a legendary monster truly memorable is its character. Take the demon lords from Out of the Abyss. Mechanically, there are a lot of similarities between them all, but each has maybe half a dozen unique abilities that help distinguish one from the other. These are often an attack or two, an interesting trait, and are frequently found in lair actions and regional effects. Briefly, let’s compare Graz’zt and Baphomet. One is a master tricksters and manipulator, the other is the embodiment of bestial wrath. Graz’zt has the shapechanger trait, access to spells like dominate person, the ability to teleport in three different ways, and to move other characters around. His lair actions and regional effects are all based around charming, confusing or otherwise tricking the players. In direct contrast Baphomet has the charge and reckless traits, has three different attack options, and even more attack options in his legendary actions. Not only this, he has traits which are typical of a minotaur-type creature; labyrinthine recall, access to maze and wall of stone, and lair actions/regional effects that amplify these effects. Here you can easily see that just a few differences in obvious things can truly define your monster, and help make it a BBEG to be remembered. All of these can be emphasised through the roleplay of the monster, but when designing your statblock, making these unique, thematic elements clear can help to guide those interactions.Below I’ve included some high CR monsters I’ve made for adventures, including Laogzed from the Cult of the Glutton adventure I talked about earlier this week. Hopefully these statblocks illustrate what I’ve talked about in the article! Let me knwo what you think, and show me your legendary monster statblocks!