While working on projects at work today I had a sudden thought when thinking about creating homebrew beasts for the moon druid in my campaign. We had talked previously about the lack of options at CR 3 when they reached level 9, and while working on it today came to the idea that for my homebrew world it would make sense for moon druids to have their wild shapes "evolve" in some way. Primarily this meant increased combat effectiveness for more damage, HP, etc. Instead of keeping it to myself, I figured I would post it here to see what everyone else thought and if you like it, to use in your own campaign! I plan on making quite a few "evolutions" for different beasts for my own records, so if anyone is interested I can make those public here on Beyond as well.

The first portion of this was to solidify how I would have a druid start with wild shapes in my game, which is pulled from XGtE's table in the Wild Shape section. References to the world and locations can be easily swapped out for official settings or your own. 

(Also, if someone already had this idea, none of this was taken from that! I did a search through the forums and didn't find any homebrew rules here that went into wild shapes, though there most likely is something out in other forums.)

Druid Forms and Evolving Wild Shapes

In Aynerth, the affinity of druids ties them directly into the beating heart of the world and all the living creatures that inhabit it. This affinity is directly tied to beasts of all shapes and sizes, and each region a druid hails from directly influences what beasts they have interacted with.

Druid Forms 

If your character is a druid, your known animal forms are based off a particular type of region, such as the grasslands, mountains, coast, or desert. Xanathar’s Guide to Everything has a section listing beasts by CR in each of those, and other regions. Upon reaching 2nd level, choose one of those regions that best describes the area you knew best before adventuring. You have the knowledge to transform into any of those beasts when allowed to do so by the rules of Wild Shape.

While adventuring in different regions, you can ask the GM to perform a task, “Observe Nature”, while traveling to learn new animal forms.

While dinosaurs exist, not many that live in regions without dinosaurs know of them. If your druid is from any other region aside from the tropical islands of Hawash, or continent of Freylur, you are not able to Wild Shape into a dinosaur without discovering it from the Observe Nature task.

Observe Nature

Over the course of 7 days, you can focus on observing the wildlife that inhabits the region you are traveling or staying in. While performing this task, you are unable to perform any other tasks during travel, such as scouting, foraging, or tracking. At the end of that amount of time, make a Wisdom (Perception) check and an Intelligence (Nature) check. Based on your results, you will gain additional beast forms for your Wild Shape feature from animals that inhabit the region. If a region does not contain any animals that you have not previously observed, you will learn so after 3 days, are not required to make any ability checks, and learn no additional wild shape forms. The days performing this task do not need to be consecutive.

Evolving Wild Shapes. More so than other druids, as a circle of the moon druid you are more connected with animal life and your ability to transform grows over time. When choosing the druidic circle at 2nd level, select two from the list of available forms for the region you have chosen for your wild shapes. These become your evolving wild shapes that increase in power while you grow as a druid. If these shapes are less than a CR 1, you learn a form of that beast that is a CR 1. You still retain the ability to transform into the original version of that beast. When your Circle Forms feature increases the maximum CR of your wild shape, your evolving wild shape increases to match that CR (2 at 6th level, 3 at 9th level, etc).

Keep in mind the following limitations when selecting your evolving wild shapes:

• Most shapes will grow in size at higher CR, but no larger than a Large creature.
• Beasts will normally only gain the Multiattack action at CR 2 or higher, with a select few at CR 1. If a creature does not have, or gain the Multiattack action, they will have another trait that increases combat efficiency.
• It will not gain additional senses or traits, such as keen sense or darkvision, when at higher CR.

For DM’s

The evolving wild shape feature can potentially put more work on you when away from the gaming table if you have not already created new beasts at these higher challenge ratings. If either you or one of your players wish to use these optional rules, sit down and have a discussion to lay out what the expectations are. If the player is adept at creating monsters that are in line with existing ones, or can make a new one following the rules for creating monsters from the Dungeon Master’s Guide, let them do the heavy lifting of creating their evolving wild shape for the different CRs and make any necessary adjustments later.

If you prefer to create them yourself to maintain balance with your interpretation of the rules, compare the increase in strength from the Black Bear to Brown Bear and then to Polar Bear, or the Wolf to Dire Wolf, or Eagle to Giant Eagle as references.