Argthtjtr

In my current campaign, I introduced a crazy scientist that uses mutagens in order to transform into different monsters. It’s really cool and really creepy. One of the characters in the party recently died and the corresponding player would be interested in playing a character similar to this NPC I introduced. His new character would be the scientist’s apprentice, who realized that his master is an evil psychopath, and now joins the party to do some hero stuff.

Long story short: I would like to offer my player the opportunity to play this kind of character, but I haven’t found a satisfying way to implement this concept with the available/official material and I’m not a fan of inventing a whole new class or subclass. So, I was looking for a simple solution and I came up with a variant of the druid class. Only slight changes are necessary, so I think it should be balanced:

• Armor, weapon and saving throw proficiencies stay the same




• Same skills to choose from




• Alchemist’s supplies instead of herbalism kit




• Wild Shape would function the same, but instead of transforming into
  beasts, this character would transform into monstrosities




• Spellcasting like a sorcerer (spells known, etc.) with the sorcerer spell list, instead of preparing spells like a druid from the druid spell list. Wisdom would still be the spellcasting modifier.




• Instead of Druidic as language, this character would be able to
  converse with monstrosities in their own language (e.g. Otyugh, Worg,
  Umber Hulk)

Obviously, not all druid subclasses would make sense with these changes to the core class, but I trust my player to choose a reasonable one. So right now, it's just about the core class.

Is this Variant Druid balanced, compared to the regular druid class? Or am I overlooking something that will absolutely bite me in the ass?

Spellcasting

The sorcerer spell list is significantly more damage-focused than the druid list, which tends towards debuffs and utility spells. That doesn't make it inherently unbalanced as such, but it might be of concern. I might suggest using the druid list, and if there are a couple of specific sorcerer cantrips or spells that seem particularly apt for the character, add them to his list, rather than just switching out the entire spell list. It only takes one or two cantrips to give the character a unique flavor, without going to the extreme of rewriting the whole class list.

Wild Shape

Switching Wild Shape into, let's call it "Monster Shape", is a tough question. Honestly, it really does depend on which subclass he takes, because a Moon Druid's expanded CR choices will make all the difference.

A non-moon subclass may find the monster choices very limiting, because there just aren't that many weak monstrosities that don't have a fly speed. I think you'll find that at 2nd level (CR 1/4) he'll have no valid choices, and only a handful at 4th level (CR 1/2). This may, of course, change with future book releases. Once he hits 8th level there are maybe a few interesting Monster Shape forms, but still very limited, and weak for that level to boot. A normal non-moon druid at that level tends to use wildshape for utility effects rather than to get cool combat forms, and some of that utility will be lost just because a Darkmantle or whatever is a lot more notable than a raven, rat, or even bear.

Using Circle of the Moon adds quite a few forms. It's still very limited, but maybe not so bad; the big issue there is as you level up, you'll be adding monsters with bizarre abilities to the list, some of which are fine for their CR in the context of a single fight but may be gamebreaking if a PC can just use them any old time he wants. Most of the really bad stuff is forever out of reach, but at higher levels you will see stuff like Lamias, Gorgons, and Medusae coming into play. And Mimics are in at 6th level, which all by itself might give you pause.

So what can you do? Well, I feel people often try to over-complicate things by rewriting huge swathes of rules text to fit with a weird idea, rather than taking the safer and easier path of reskinning the existing rules with new descriptions to match the flavor of what they want to do, and possibly making one or two little tweaks when the mechanics don't quite work as written.

My suggestion in this case is to use Wild Shape as it's written, but change the flavor by reskinning each of the Beast forms to describe some quasi-human monstrosity instead. A dire wolf becomes a hulking wolf-man. A giant eagle becomes a harpy or even griffon form. A warhorse form is described as a centaur or minotaur, a brown bear is an owlbear or half-troll, a giant bat is the Man-Bat from DC Comics. Whatever. I think that sort of thing could easily give you the flavor of turning into bizarre monsters without getting into the mechanical difficulties of the actual Monstrosity creature type. (You'll still have the roleplay effects of being a gross monster rather than just a regular horse or what-have-you, so this might work best if he goes for Moon druid.)

The only mechanical changes that might come up are whether some monster forms can talk or use their hands, but even then it's less common than it might look. A giant wolf-man that's secretly a direwolf probably can't speak like a human, just growls and howls, and his massive clawed hands could easily be useless for anything but the most basic grasping that a wolf's muzzle could accomplish just as easily. You could have his forms use the "monstrosity" type rather than "beast" -- the only real game effect there is immunity to a tiny list of spells and effects. ("Animal Friendship" and "Dominate Beast" are the only ones that really come to mind, off the top of my head, and those can be largely duplicated by higher level spells -- they're just easier to get to if you're targeting a beast.)

It looks mostly fine to me, though it’ll be worth looking at the monster lists as there are far fewer monstrosities than beasts that fit the Druid restrictions - only 21 in my collection on D&D Beyond (that includes the main monster books, plus a few from adventure). There’s less variety in terms of size, for example, and monostrosities can’t get around without drawing attention the way many beasts can.

In addition, while beasts rarely get powerful supernatural abilities, monstrosities do - for example being able to turn into a Rust Monster might give the player quite an advantage against humanoid foes armed with metal weapons, and a Cockatrice can petrify those it bites - something balanced against PCs who might have resources to resist or recover from this, but which might be overpowered when used against monsters.

These abilities might also offset the lack of spellcasting when using wild shape, another balancing factor, moreso than the charges, pounces and multiattacks that beasts typically get.

Are you sure this is a druid?...

While I don't think it's unbalanced, I think it's too divergent from what a druid is supposed to be about - nature. Furthermore, the sorcerer aspects don't really match with the idea of a "scientist". That strikes me as something more wizard-like, very Dr. Jekyll and Mr. Hyde, rather than anything druidic.

I’m not a fan of inventing a whole new class or subclass.

Making it a subclass rather than messing with the base mechanics of an existing class is actually a better, perhaps even simpler option. If I were to create such a character, I'd probably look at porting some of the wildshape mechanics (including your monstrosity choice) over to a Wizard subclass.

If it's gotta be a druid...

If you're dead set on Druid, I would still do it as a subclass. Don't mess with the spell casting, that's your biggest potential imbalance point. Sorcerer spells tend to be direct damage, while Druid spells tend to be lower damage but more subtle, or have support effects.

Go ahead and give them Alchemist Tools proficiency for free when they pick up the subclass; one bonus tool isn't going to matter much.

However, monstrosities tend to be have strange abilities. One of the balance considerations to take into account is how often they'll get to use them. Many of the creature abilities become more powerful when they're regularly available - they're designed with creatures that end the encounter dead in mind. With that in mind, I'd base your Monstronity Shape ability on the Circle of the Moon, with a few changes.

• Don't take away the basic druid's beast abilities; there aren't many good monstrosity choices at lower CRs.


• 
  Combat Wild Shape could stay the same, but due to the special effects available to monstrosities, I would probably drop the bonus action transformation part. A slight delay in the power up phase will balance out those special abilities to some degree. Keep the healing, perhaps combine it with giving them alchemist proficiency and call it Alchemical Enhancement or something to that effect.


• 
  Circle Forms stays the same, except that it adds higher CR monstrosities not higher CR beasts. The character will retain the utility function of the normal, lower CR beasts, but ends up with a narrower range of monstrosity forms. Call it Monstrosity Forms instead.


• 
  Primal Strike is fine, maybe call it Alchemical Strike for flavor's sake.


• 
  Elemental Wild Shape is a bit problematic for the theme. My initial thought was to add a few aberration forms, for extra weirdness, but there weren't many good choices to match the CR 5 of the elemental forms. In the absence of anything better, I'd just leave it as-is.


• 
  Thousand Forms doesn't need any changes, other than perhaps calling it Alchemical Adaptation or something like that.

It doesnt look like anything about this would cause issues. And the spell casting ability and etc isn't a huge bonus other than the fact that they are all used on different things.

In the end it comes down to what type of player this person is and if you can trust them not to try to exploit it.

It doesn't matter how balanced you try making something if someone really wants to they can break it.

You can spend hours and hours balancing it just for it to be unnecessary because its just a player happy to be playing something theatrically fun.

To save yourself some time just talk to the player and see how basic or complex they want it

If you want to allow them to turn into monstrosities, or theatrically change the forms they are using. Instead of actual "monstrosities" re flavor the wild shapes to theatrically look monstrous.

For prepared casting have it work like a druid but they are Instead of communing with nature getting vials and flasks and filling them with strange chemicals that they mix together to make spells.

** Talk to the player and see if they would like to theatrically re flavor moon circle druid with sage Alchemist background to instead be a mutagen scientist apprentice **

If they are only wanting the thematic and role play of the scientist then here it is just re flavor and rename things. If they want mechanically different then make subtle changes like what you are.

Don't be scared to say yes to something if its for flavor and fun with no statistical differences or advantages.