Pact of the Eye.

An eye has been bestowed upon you by your otherworldy patron it is placed in a random location by your otherworldly patron but it is most often put on the forehead, as an action you can focus to look through this eye and while you do so you can see into the astral plane for up to 30 feet. Additionally you can spend an action to learn the nature of a humanoid creature you can see within 120 feet with an Intelligence of 6 or higher. You learn its alignment and its most prevalent moral or behavioral tendency (violent, altruistic, aloof, etc.). Additionally, you gain advantage on the next Insight check you make on the creature within 1 minute, after which the target is immune to this ability for 24 hours. You can use this feature a number of times equal to your Charisma modifier, and regain all uses when you complete a long rest. (Credit to /u/SabotageThis from whom I stole this ability)

Your Pact Boon Your pact with your patron may influence the appearance of your Eye. Some forms your Eye could take may include:

Archfey: A uniquely colored eye such as one with bright green Sclera, Magenta colred Iris and a white Pupil.

Celestial: a pure golden eye, no iris or pupil that glows with pure radiance.

Feind: a Goat eye.

The Ghost in the Machine: A mechanical sensor.

The Great Old One: a simple pure black unblinking eye that oozes squid ink occasionally

The Hexblade: a rune vaguely in the shape of an eye

The Raven Queen: The eye of a raven

The Seeker: A glowing star.

The Undying: An empty eye socket

Eldrich Invocations At 2nd level, the warlock gains the Eldritch Invocations feature. Here are new options for that feature, in addition to the options in the Player's Handbook. If an Eldritch Invocation has a prerequisite, you must meet it to learn the invocation. You can learn the invocation at the same time that you meet its prerequisite. A level prerequisite refers to your level in this class.

All seeing eye Prerequisite: Pact of the Eye

You gain proficiency with Perception and Insight.

Hunters Sight Prerequisite: Pact of the Eye

You can cast Hunters Mark at will without expending a spellslot

Vision of Guidance Prerequisite: Pact of the Eye

You can cast Augury at will without expending a spellslot or requiring the material components once per short rest.

See the unseen Prerequisite: Pact of the Eye, 5th level

You may cast See Invisibility Once using a Warlock spellslot

Eye on the Target Prerequisite: Pact of the Eye, 7th level

You may cast Clairvoyance will without expending a spellslot once per short rest.

Sight Beyond Sight Prerequisite: Pact of the Eye, 15th level

You may cast Scrying at will without expending a spellslot once per short rest.

Eye Beam Prerequisite: Pact of the Eye, 5th level

You may cast Scorching Ray Once a day using a Warlock spellslot, this Scorching ray deals physic damage not fire.

Feindish Insight Prerequisite: Pact of the Eye, Pact of the Feind

As an action you designate a target within 120 feet of you, they must make a Wisdom saving throw (The save DC being your spellsave DC) on a success the target has no idea you have done this and you gain a knowlage on how best to talk to them, for the next minute you have advantage on persuasion checks against the target. on a failure the Target knows you have just tried to enter its mind and will become hostile