Your patron is a high ranking Angel of a Deity pantheon, who represents unwavering absolutes. They have no concept of deception and seek truth, justice and law, in whatever form that takes. Beings of this sort include the Lawful angels of Mount Celestia, known as Archons, the Chaotic good Angels of Arborea, the Valkyrie of Valhalla or the Guardinials of Elysium.
Angels often employ the use of mortals, as they are created without basic free will; they are instruments of some divine entity and need the creativity that comes from mortal thought processes. Similarly, you may be chosen as some kind of prophet to deliver a message to the mortal races of the world.
Expanded Spell List
The Archangel lets you choose from an expanded list of spells when you learn a warlock spell. The following spells are added to the warlock spell list for you.
Archangel Expanded Spells:
1st Level: Bless, Cure wounds
2nd Level: Prayer of Healing, Zone of Truth
3rd Level: Beacon of Hope, Mass Healing Word
4th Level: Divination, Guardian of Faith
5th Level: Mass cure wounds, Raise Dead
You are a fount of healing energy and can heal the badly injured. As an action, you can restore creatures a number of hit points equal to five times your Warlock level. Choose any creatures within 30 feet of you and divide those hit points among them. This feature can restore a creature no more that half of it's hit point maximum. You must finish a short or long rest before you can use this ability again.
Starting at 6th level, you can pray to your patron to alter fate in your favour. When you make an ability check or a saving throw, you can use this feature to add a D10 to your roll. You can do so after seeing the initial roll but before the roll's effects occur.
Once you use this feature, you can't use it again until you finish a short or long rest.
Beginning at 10th level, you can call on your patron to intervene on your behalf when your need is great.
Imploring your patron's aid requires you to use your action. Describe the assistance you seek, and roll percentile dice. If you roll a number equal to or lower than your Warlock level, your patron intervenes. The DM chooses the nature of this intervention; the effect of any warlock spell would be appropriate.
If your patron intervenes, you can't use this feature again for 7 days. Otherwise, you can use it again after you finish a long rest.
At 14th level, you gain the ability to sprout a pair of wings of pure light from your back, gaining the ability to fly at a flying speed equal to your current speed. You can create these wings as a bonus action on your turn. They last until you dismiss them as a bonus action on your turn.