Circle of the Barren Lands

Druids of the Barren Lands have either spent a long time or grown up in harsh environments where monstrosities as much as beasts are a part of every day life. They have studied the monstrosities and their bestial origins to learn how to adopt their wild shape in to their forms. 

Those that study this path become corrupted, typically neutral or evil alignments. Drow, Duergar and Deep Gnome's have a special affinity for this perversion of druidic practice. The push to get these abilities is more about using the natural world for your benefit than it is the study and harmony of nature. 

Monstrous Forms

 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, while you are transformed by Wild Shape, you can use a bonus action to expend one spell slot to regain 1d8 hit points per level of the spell slot expended.

The study of the monstrosities allows you to transform in to powerful creatures. Starting at 2nd 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). Speak with your DM about your backstory and select some you will know to transform in to at the start of your game. You can still wild shape in to a beast as per the rules in the beast shapes table.

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.

Monstrosity Familiarity

You gain advantage on survival checks to track monstrosities when you reach 3rd level

Penetrating Strike

Starting at 6th level, your attacks in monstrosity form can add a magical effect to any non magical attacks. Should you choose to implement this roll a d4 and normal damage becomes one of the following.
1 - Fire
2 - Necrotic
3 - Acid
4 - Cold

Colossal Transformations

At 10th level, you can expend two uses of Wild Shape at the same time to transform into a Banderhobb, Bulette, Gorgon or Young Remorhaz

Unnatural Power

By 14th level, you have learned to use magic to improve yourself or your allies skills. You can cast the Enhance Ability spell at will but can only have it active on one target at a time. It does not require concentration when using this feature.