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Building Legendary D&D Monsters in your Head

by Mike on 30 December 2019

Here at Sly Flourish I believe firmly in helping DMs develop the tools change up our game without having to spend a lot of time or carry around a lot of extra books. This means learning how to do a lot of the prep and improvisation work of D&D in our heads. For example, my encounter building guidelines are intended to give DMs some rules of thumb to quickly gauge whether an encounter might be inadvertently deadly.

We have other tricks we can use to improvise the challenge of a combat encounter without resorting to any charts, tables, tools, or anything else. We can increase or reduce a monster's hit points, damage, or the number of monsters in a battle to easily change the threat of the battle. We can do all of these while a battle is taking place. If this feels like cheating to you, consider hanging onto the game with a looser grip. As long as your drive is to make the game as exciting as you can, you have full authority to make these sorts of changes.

We have other simple tools we can keep in our heads that help us run a fun D&D game. We can grant advantage or impose disadvantage as we improvise the situations, actions, motivations, backgrounds, and specialties of the characters. "Bless, roll an Intelligence (Religion) check to see if you recognize some of the symbols on this altar. Roll with advantage because the voice of the planetar in your sun blade whispers ancient secrets to you,".

Improvising difficulty classes (DCs) is probably the most-used and easily-implemented improvisation techniques in D&D. If there is a reasonable chance for failure in any situation, choose a difficulty based on the situation on a number between 10 (moderately easy) and 20 (really hard). That's the challenge the characters must beat.

Improvising Legendary Monsters

Now we come to the subject of this article; building legendary monsters the lazy way. Much of the time we can use an existing legendary monster from the Monster Manual. Probably 19 times out of 20, this suits us just fine. Sometimes, however, we want to take a normal monster and make it a legendary one. Let's take the Avatar of Sekolah for example. The Avatar is a giant two-headed shark summoned by the priestesses of the sahuagin. There's actually a stat block for this shark in Ghosts of Saltmarsh but I wanted something more straight forward and dangerous.

We start with the giant shark stat block in the Monster Manual. The first thing we can do to make this thing legendary is to increase its hit points—200 sounds good. Again, no need to write anything down. We just keep this in mind. Now we get on to the legendary parts. First, we give it three legendary actions. These might be used for an additional attack, a move, or some other activity that makes sense. In the case of the Avatar of Sekolah, we'll give it an extra bite attack as part of its attack action to account for its second head (oh yeah, it has two heads). We can also give it an extra bite attack for the cost of two legendary actions and a free movement without provoking attacks of opportunity as a single legendary action. This gives it some mobility and a way to threaten back-line combatants. Finally we give it three uses of legendary resistance to break out of save-or-suck abilities.

All of these things can be done in our head. We don't need to write them down. This lets us turn any monster into a legendary monster without having to do any real work at all.

Announcing Legendary Monsters

Because it might not be clear that the characters are about to face a legendary monster, it can help to announce to them that they are about to face a legendary foe. I like to say "you believe you are about to face a legendary foe" while wiggling my eyebrows. This gives the players some opportunity to shift their tactics and they won't be too unpleasantly surprised to find their save-or-suck spells getting ignored and the monster they're facing hitting them between turns. Some DMs believe this information should be held behind the screen. I don't mind revealing it and I've never seen it detract from the fun of the game.

When in doubt, lean towards revealing too much.

Don't Overdo It

Just because we have easy tools to build legendary monsters doesn't mean we should use it often. Legendary monsters are truly special beings. A legendary monster is more than just a stronger variant of an existing monster, it's a unique variant. If we want a stronger monster, more hit points, more attacks, and more damage will often do the trick without giving them legendary actions or legendary resistances. Legendary monsters are special. Our players should never question why this creature is legendary. One mere look at it and the story surrounding it should be enough to mark its legendary stature.

Worry Less About Challenge Ratings

One argument about building such legendary foes is that these changes increase the challenge rating of the creature and we don't know how far. My simple response is "It doesn't matter". Challenge ratings are a loose guideline at best. What we know of the capabilities of the characters matters much more. Given that we're taking a single creature and making it legendary means we're likely only running that one creature. This puts it at a distinct disadvantage against four to six characters already. It's challenge rating may be two or three higher than the original but really, who's counting? If you double the hit points of a creature and give it legendary actions and resistances, you can probably count it as two or three copies of the base creature.

Better yet, don't get hung up on the math; it doesn't work that well anyway.

Building a D&D Toolbox We Keep in Our Heads

The best tools in D&D are the ones we have in front of us. Even better are those we need not have on hand at all but can keep in our heads. The ability to build legendary monsters without having to write a single thing down is a powerful tool in our toolbox. We can turn any creature into a creature of legend—a creature whose name will be recorded in ancient texts and fantastic stories. Keep these guidelines in mind when you wish to build your own legendary foe.