Nothing helps create flourish in a homebrew campaign setting like unique experiences. Everyone in my group is familiar with my campaign settings. When I throw them "Warpling" demons and Shadow Sorcerers, they are reminded who's universe they are in. Those creatures are to my campaign what the Uruk-Hai are to Lord of the Rings, White Walkers are to Game of Thrones, or what Dementors are to Harry Potter.
It's that extra bit of flavour that instantly reminds your players where they are adventuring. Sometimes this can be as simple as reskinning a monster. Many game masters find it fun to create a new monster from scratch (whether it's a completely new monster, or even a modification to an existing monster). Maybe you want to revamp your Orc faction by creating an Orc who wields two maces, called an Orc Juggernaut. Or maybe you want to create a whole new monster to assist your kobold dungeon defenders by creating a hydrake (a drake with five heads).
It may also be useful to note that customising (or even re-skinning monsters) can help with both conscious and subconscious metagaming. It's always handy to keep the players on their toes. Even if they are not trying to metagame, somewhere in the back of their minds they'll have preconceived ideas about how to position/attack certain types of monsters like Grells or Mind Flayers. But if you put in little twists or custom monsters, you could even catch them off guard!
I have a few tips to help you when you are creating some dangerous monsters. I hope these will help you on your way to adding many memorable moments to your homebrew campaign, or even a surprise twist as part of a published adventure!
1. Who Are The Monsters With?
Think about where your monster fits into the world. Think about what faction they will be with. Would they be raiding alongside demons, or guarding an undead tomb? Think about what kind of monster they are. Think about who they would be working with. You can look at the factions that are in your campaign and the monsters and build them together logically.
I like to do lists, per faction, of the different monsters that are in that faction. So my undead faction, The Legion, has skeletons, zombies, ghouls and vampires. I’d list all these enemies, for all my factions. This allows me to look at each list and see which faction needs some more units in its arsenal. Let’s say my demon faction only has three monsters on its list - it’s a bit empty, so I would think about another demon-themed monster or demon ally.
An ice golem wouldn't hang around a group of fire demons in a volcano; they'd melt! Similarly a monster working alongside Medusa would either be blind or have something that makes them immune to petrification. So make sure that you use this line of thinking when considering adding monsters to a faction. By adding with theme in mind, you can further immerse your players.
2. Where Does The Monster Fit in Their Faction Hierarchy?
Think about why the monster is part of the faction. What role do they fill? If an Orc tribe uses dire wolves and giant bats for reconnaissance, tracking, flanking, and otherwise quick-reacting support, then they probably wouldn't also use Displacer Beasts, giant spiders, and Stirges too, as they perform the same roles.
When creating a new monster, make sure that it has a reason for existing. It has to bring something to the table, the goblins don't train wolves for fun, they train them to use as fast, mobile units. Ensure that your custom monster which serves as a bodyguard for a dragon, doesn't step on its master's toes by solely using a breath weapon and claw/bite attack.
Look at the list of monsters in that faction. What is it lacking? A powerful goblin clan might lack big tanky enemies - in which case you could throw in bugbears, trolls, etc. Or maybe if they are industrial goblins, they could create automatons as custom monsters that fulfill the same role!
3. What Makes Your Monster Cool?
What makes your monster memorable? Giving an Orc two maces instead of an axe isn't enough. They need something on top of it. Give them cool abilities, unique traits, something that the PCs will remember, both during and after subsequent sessions. ("Oh crap, not the crazed blue-orcs with the double maces!" your PCs might say.)
Maybe the orcs with blue blood are far more brutish and barbarian-like than their green-skinned brethren. It's very easy to portray this with a few little unique traits. "Whenever the blueskin scores a critical hit with a weapon attack, the PC must pass a strength save or be stunned." Then "every time the blueskin takes an instance of damage, increase his own weapon damage rolls by +1." You could even provide him an ability from the Barbarian class to make them more memorable.
You can really go to town with giving creatures abilities or traits to really define them, and make them cool and memorable. Maybe pyro goblins are infused with the power of a fire elemental, giving them fire resistance, and a 1/day use of a fire breath attack (which uses a level 1 burning hands spell effect). Perhaps the Orc chieftain can use his reaction to attack a PC that hits him in melee. Don't be afraid of adding things that give monsters a unique or cool factor to them.
4. Is Your Monster Fun to Fight?
Some monsters are cool, yes, but are they fun for the PCs to fight? Think about ways to change that. Ensure that you are aware of abilities and traits that take away player agency and abilities, and make sure that you use these in moderation. Having an enemy wizard with shield and counterspell isn't too bad as an infrequent boss, but having 4 straight encounters with counterspell-wielding enemies will frustrate your spellcasters immensely.
Another thing to look at when deciding whether something is fun to fight is the amount of time a combat with this monster would take. For example, a monster that forces saving throws constantly will slow down the game. Too much of this can make encounters less fun. Be careful with monsters that can force multiple saves, have multiple complex legendary actions, or other abilities that can slow down the game too much.
When making monsters, put yourself in a PC's pair of shoes. Is this monster fun to fight? If it's too boring, too disruptive (disruption is fine in moderation), or too controlling, or too time demanding, then you should take note of this and make adjustments accordingly. These adjustments can either be made to nerf or rework some of the abilities, or you can simply use these monsters more infrequently, or in specially designed encounters to balance out the encounter a little.
5. Expect the Need For Modifications
Nobody can expect every custom monster they create to be perfect from the moment they hit the battle grid (or the mind theatre, depending on how you play your D&D). Expect that your monster may be more or less powerful than they look on paper. Ensure that you make adjustments either after the encounter or during, to nerf or buff as needed. Perhaps their abilities aren't working the way you wanted, in which case you may need to rework them for future battles. Or you can just drop it completely and modify it for use in the next campaign in a few months/years time for a good re-release of the monster.
Either way, never feel disappointed if a monster isn't quite as powerful as what you wanted, or if it is too powerful when you first release it on your PCs. Fine tuning is a very common thing here. While experience definitely helps, the bottom line is having the stats on paper is only the start. You will need to see it in action before you can really judge how it goes.
I hope that this guide is useful in giving you tips that help you start, or improve, your custom monster creations. The only true way to improve is practice, but sometimes all you need is a little bit of motivation and inspiration to start creating some little critters.
Peter is an avid dungeon master, role-player, and story teller. When he's not running homebrew campaigns, he is creating new worlds, or he is reading and writing fantasy stories, forever immersing himself in the gaping black-hole known as the fantasy genre.
I am become death, destroyer of worlds.