Circle of the Guardian

Druids of the Circle of the Guardian are bound to protect nature and its inhabitants. Usually found around sites of great natural significance, a Guardian takes the form of a hulking creature to destroy their enemies and protects what they hold dear. Many Guardian Druids wander the world for long periods of time, seeking a better understanding of the dangers their forest realms may face.

Guardian Form

Instead of relying on the variety of forms, a Circle of the Guardian druid has worked tirelessly to master one form. This form can take an appearance you choose, although the common form taken by Guardians is that of the bear or a stag. When you use your Wild Shape feature, you are able to shapeshift into the Guardian Form.

Note: Because I cannot link to other homebrew through this subclass due to the rules of D&DBeyond, you can find this form and all of its variants published by me under homebrew monsters. The forms this subclass makes use of are as follows: Guardian Form, Ferocious Guardian Form, Dire Guardian Form and Defender of the Wilds.

Thorns

Beginning at 2nd level, when you are in your humanoid form or in one of your Guardian forms, you may use a bonus action to expend a spell slot and make your exterior sharp and thorny. For 10 minutes after you use this feature, anyone who makes a melee attack or melee spell attack against you takes piercing damage equal to the level of spell slot you expended.

Using this feature with a 3rd level or higher spell slot gives you resistance to non-magical damage for the duration. Using this feature with a 6th level or higher spell slot gives you resistance to bludgeoning, piercing and slashing damage for the duration. Using this feature with a 8th level or higher spell slot gives you resistance to all damage types for the duration.

Omen of Clarity

Beginning at 3rd level, while in Guardian form or any of its variants, you are able to cast the faerie fire and entangle spells. The vocal components of this spell become a fierce roar. The somatic components required for these spells can be performed in your Guardian form and no material components are required. These spells must be prepared to use.

At 6th level, you can cast barkskin and moonbeam in this way. At 10th level, you can cast conjure animals in this way. Finally, at 14th level, you can cast dominate beast in this way.

Finally, at 6th level, once per Long Rest, you may cast one of these spells as a bonus action, rather than an action. At 14th level, you may do this twice per Long Rest.

Ferocious Guardian Form

Upon reaching 6th level, your Guardian Form becomes the Ferocious Guardian form. This form is more powerful and gains access to new abilities. This form replaces Guardian Form.

Dire Guardian Form

Upon reaching 10th level, the Circle of the Guardian Druid attains a form considered to be a dire beast, a monster of immense power, the Dire Guardian Form. This form replaces Ferocious Guardian Form.

Defender of the Wilds

Upon reaching 14th level, your Guardian Form now grows with you. This form, the Defender of the Wilds, replaces Dire Guardian Form. Your HP while in Defender of the Wilds form is equal to your Druid Level + your Constitution Modifier, multiplied by 5. While in Defender of the Wilds form, you have a number of d10 hit dice equal to your Druid level. Additionally, while using the barkskin spell in Defender of the Wilds form, your AC can't be less than 18.