You've learned how to best alter your shadow to help those around you and impose pressure on your foes.

Shadow Magic

Ranger Level	Spell
3rd	Bane
5th	Pass Without a Trace
9th	Phantom Steed
13th	Evard's Black Tentacles
17th	Passwall

Shadow Extension

Starting at 3rd level, you gain the ability to extend your shadow to slow others movements and lessen the effectiveness of their attacks. As a bonus action, you can force a target up to 60 feet away from you to make a dexterity saving throw against your spell save dc. On a fail, your shadow extends to their feet for 1 minute. Creatures affected by your shadow have their movement speed decreased by 10 feet and the first attack on each of their turns has disadvantage. If you use this feature while a creature is already affected by your shadow you can extend your shadow to another creature up to 30 feet from that creature.

Once you use this feature you can’t do so again until you finish a long rest, unless you expend a spell slot of 1st level or higher.

Doppelganger

By 7th level, your shadow has become so strong that you can give it mass and form. As an action, you can cause a misty black form to appear up to 30 feet from you. Any action or movement you make is mimicked by the doppelganger. If this doppelganger is attacked the form shifts around the attack and is unaffected. As a bonus action, you can move this figure up to 30 feet. The Doppelganger can pick up up to 10 pounds, if it attempts to pick up any more it pushes through its form and falls to the ground. If you attack a creature while your doppelganger is within 60 feet of the target of that attack (or 5 feet if you're using a melee weapon) the target takes an additional 1d6 psychic damage. The Doppelganger vanishes after 10 minutes or when you use this feature again. If you target this with Shadow Extension you can target 2 additional targets up to 60 feet from your Doppelganger.

Dark Terrain

At 11th level, you gain the ability to stretch your shadow to its absolute limit for a split second. You can use your action to instantaneously spread your shadow out 8 miles around you for a split second. For 8 hours after you use this feature the terrain around you becomes one of your favored terrains and up to 1 creature type found inside becomes one of your favored enemies (you do not gain any additional languages due to this feature).

Once you use this feature you cannot use it again until you finish a long rest. Unless you expend a spell slot of 3rd level or higher.

Shadow Storage

Starting at 15th level, as an action you can have a creature that is up to 60 feet away from your shadow make a dexterity saving throw against your spell save dc on a fail you store your doppelganger in that creatures shadow (if they don't have a shadow they gain one even if invisible). You can pull the shadow back out as an action as long as the creature the shadow is affecting is within 90 feet of you. While a creature is affected by this feature you always know their exact location and on each of the creatures turns the Doppelganger can make a melee attack against the creature with a +7 to hit. On a hit the target takes 3d6 + your dexterity modifier psychic damage and makes a constitution saving throw against your spell save dc to get rid of the shadow. On a success your shadow dissipates but you can always recall the last spot it was in before it vanished.