Monster Mash

By Ian on 12 March 2023.

Whether it’s a stick-wielding goblin or a raging pit fiend from the depths of Nessus, the monsters of D&D come in all shapes and sizes. Oftentimes this makes it easy for a DM to find the perfect beasty fit for almost any encounter. However, there are some cases where it’s best to look beyond the Monster Manual. Perhaps you’re DMing for experienced players and are looking to challenge them with an abomination none of them have faced before, or maybe you have been wanting to use a creature that is not found in your campaign’s environment. It’s times like these I enjoy using a DM technique I call the Monster Mash. 

This is done by mixing a base monster with one or more other ingredients in order to create a new creature. The most common ingredients used in this process are:

• Another monster or animal
• An element or environment
• A class or background from the Player's Handbook

To demonstrate the process, let’s craft a creature together using all of the ingredients above. The monster we’ll be mashing today will be the Roper. 

Mixing Monsters 

Combining monsters is not as simple as stitching two beasts together, unless you're looking to create a flesh golem. Instead, this process should involve infusing your base monster with the features or abilities of another. Ultimately, this will leave your monster with a slew of new abilities at its disposal, but be sure to have creative lore ready to describe how this abomination came to be.

• The beholder artificer had long since discarded his fleshy form. Now inhabiting a mechanical body, it seeks to rid the material plane of organic life.
• A centaur cursed by a yuan-ti blood ritual still has the lower body of a stallion, but now has the upper body of a humanoid cobra. A new breed of warrior for the Serpentine Cabal.
• Seeking to eliminate its weakness to sunlight, a vampire lord regularly ingests large amounts of troll blood. Though his experiment was a success, it left him with weaknesses of a different kind.

Let's take a look at our Roper. Even though it's able to make five attacks on its turn (four tendrils, one bite), only its bite attack actually deals damage. This means our poor Roper can easily be overwhelmed by a party's action economy. Instead, let’s splice our Roper’s tendrils with a terrifying creature from the real world: the sea lamprey.

Fusing a lamprey head to the end of our Roper’s tendrils gives it circular mouths filled with barbed teeth that latch onto prey. The tendrils can still reel targets in for the Roper’s larger bite attack, while also dealing a little damage of their own. This small change greatly increases the difficulty and tension of an encounter without the need of adding additional creatures.

Environmental Adaptation

Certain monsters are limited to specific environments or planes of existence. This can be quite the hurdle when you want to implement them into an encounter, but don’t let it stop you. Instead adapt your creature based on its new environment, changing its abilities to fit its new habitat. The creature may have learned to use this terrain to its advantage, allowing it to evolve abilities beyond those of its more ordinary kin.

• Pratorian the Sightless hatched, grew, and thrived in the depths of the Underdark. Though the black dragon was blind from an early age, he learned to hunt using his senses of smell and hearing, granting him both blindsense and keen smell. All it cost him was his eyes.
• The sahuagin of the Copper Sands grew to live on minimal water, instead burrowing to survive on the moisture found deep under the shifting dunes. Often coming up to hunt during the cold nights. They evolved and gained burrowing speed plus tremor sense. 
• A treant growing in the Underhallow becomes overgrown by fungi and an unlikely symbiotic relationship begins. The fungal infection allows the treant to throw spore clusters that create poisonous clouds. Also, instead of awakening trees, the fungal treant is able to summon myconids.

Moving back to our Roper, we find it in a frozen fortress long abandoned by its draconic residents. With not a single stalagmite in sight how can the poor Roper hope to hide? Adaptation is needed if this Roper is to survive. Instead of relying on stalagmites, let’s say our Roper has adapted to hide among a series of large icicles. Now, our Roper has evolved to deal cold damage and its clear icy skin causes ray spells to reflect randomly. Suddenly, this Roper is feeling far more dangerous.       

Classy Critters

As player characters earn levels, they also gain access to a plethora of powerful traits and abilities. This progression demonstrates a character's mastery of their honed craft, whether it be martial, magical, or something in between. Yet if player characters are able to learn these skills, why can’t their enemies? Giving your monster abilities from within the Player's Handbook is fair game, so long as you have an explanation handy!

• No one expected the fearsome lich would also turn out to be a professional lute player. Perhaps there’s more to this undead bard than the tales suggest.
• An unarmed thri-kreen may seem like an easy target. That is until you discover it has been trained in the Way of Four Fists by a monk.
• An insane kuo-toa wielding paladin-like abilities may convince some to worship his slimy idol, but who knows where his powers truly come from?

For the final time, let's return to our ferocious Roper. It may not have the intelligence of a wizard or the agility of a rogue, but what it does have is fury. Giving our Roper access to the barbarian’s signature rage ability will make this fight truly unique for the coming party. 

After going weeks without a proper meal, the icy Roper senses the presence of four individuals exploring its frozen lair. What the party thinks is merely dripping water is in fact the creature’s many lamprey-like mouths beginning to salivate. Too late, the party realizes the danger as the Roper enters a hunger-fueled rage. Immediately, half the group is bitten and pulled toward the Roper’s freezing jaws. 

Another memorable encounter thanks to the Monster Mash.  

In Conclusion        

Creating a Monster Mash is an effective way to challenge or surprise your players. This technique works best when DMing for experienced parties, or when a desired monster doesn't quite fit the campaign’s environment. Simply mixing an existing monster with a few ingredients can create an unforgettable encounter. 

If you have ever crafted a custom monster of your own please tell me about it in the comments below!   

Related Articles

• Monsters Abound
• Snappier Monsters Using the Bard
• Pernicious Foes Using the Paladin

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