Circle of Corruption

There are those druids that accept the truth that those which the common folk call monsters are still a part of nature. As such, these druids revere even these monstrous forms.

Monster Shape

When you choose this circle at 2nd level, you gain the ability to use Wild Shape on your turn as a bonus action, rather than as an action. Additionally, the rites of your circle grant you the ability to transform into more dangerous forms. Starting at 2nd level, when you use your Wild Shape, you transform into a monstrosity, instead of a beast, 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.

Monstrous Nature

Your monstrous nature grants you with a partial control over your form. You can expend one use of your Wild Shape as a reaction to reject changing into other forms for a number of hours equal to a third of your druid level (rounded down). While this effect is active you can't be magically polimorphed against your will.

Terrible strike

Starting at 6th level, your attacks in monster form count as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage.

Devilish Influence

By 10th level, you start to feel the call of the Infernal Plane, corrupting even more your image of Nature. In addition to turning into monstrosities, you can use your Wild Shape to transform into a fiend creature, but more intelligent creatures require something from you too. You may Wild Shape into Demon type fiends if your alignment is Chaotic, and Devil type fiends if your alignment is Lawful.

Altered Beast

Also starting at 10th level, you can expend two uses of Wild Shape at the same time to transform into a monstrosity or fiend with a challenge rating as high as your druid level divided by 2, rounded down.

Frightful Transformation

Starting at 14th level, your Wild Shape ability, the transformation is slow, uneven and unsettling. When you Wild Shape into a creature, all creatures of your choice within 60 feet must make a Wisdom saving throw against your spell save DC or become frightened of you until you revert back to your true form. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.