Circle of the Eclipse

The Dark land-weavers of the shadowfell learned to use their powers to twist nature to their will. They focus on the darkest powers nature has to offer, learning to take on the form of monstrous beasts that live in the nightmares of men.

Rather than seeking to be at one with nature, they rip power from the land, and twist it to their will.

Shadow Shape

When you choose this circle at 2nd level, you gain the ability to use Shadow Shape on your turn as a bonus action, rather than as an action.

Additionally, while you are transformed by Shadow Shape, you have advantage on stealth checks.

Dark Transformation

The rites of your circle grant you the ability to transform into more dangerous forms. Starting at 3rd level, you can use your Wild Shape to transform into a monstrosity with a challenge rating as high as 1 (you ignore the Max. CR column of the Beast Shapes table, but must abide by the other limitations there).

Starting at 6th level, you can transform into a monstrosity with a challenge rating as high as your druid level divided by 3, rounded down.

Claws of Darkness

Starting at 6th level, you can choose to replace your monstrous form's damage type with necrotic damage.

Nightmare Within

The rites of your circle grant you the ability to transform into more dangerous animal forms. Starting at 6th level, you can transform into a monstrosity with a challenge rating as high as your druid level divided by 3, rounded down.

Horrific Form

At 10th level, when you use your Wild Shape to transform into a monstrosity, each creature within 30ft must make a wisdom saving throw against your spell save DC or become frightened of you for one minute.

Frightened creatures may repeat the saving throw at the end of each of their turns, ending the effect on a success.

Mastery of the Monstrous

At 14th level you have mastered your body's ability to shift at will. 

You gain the ability to cast the polymorph without expending a spell slot or material components. 

You can use the spell to transform into a monstrosity with a CR equal to half your druid level.