Oath of the Void.

The Oath of the Void specializes in safeguarding the lost knowledge of the multiverse and the stars beyond. Similar to warlocks that pledge themselves to ancient and unknowable eldritch beings, paladins of this oath are given access to dark and ancient secrets—and then magically sequestered from them. By using their minds as a chamber of secrets unreachable by even them, they preserve the knowledge of the cosmos from prying forces while retaining a profound appreciation and memory of the natural order of the multiverse.
Paladins that take this oath (sometimes called voidknights) may be plagued by lost memories, yet remember they bear a burden of knowing too much—without understanding what it is. Some spend their lives dedicating themselves to the study and archiving of information, whereas others devote themselves to protecting the world against otherworldly forces.

Level 1 Features:

Tenants of the Void.

The tenets of the Oath of the Void are passed down through necessity by the unknowable forces preserving the fabric of the multiverse. This oath emphasizes the value of knowledge with restraint, as to know too much is to open oneself up to unimaginable powers far greater than can be reckoned.
Paladins that uphold this oath rarely recall their initiating oaths, but have an unshakable commitment to the following tenets—which they never recall learning.
Be a Safe Harbour. I am the wall against which the Astral waters break.
Be a Guiding Star. I am the light that carves through the endless expanse.
Be a Steward of the Material. I shall guard the realms of mortals from monsters beyond their understanding.
Be a Keeper of Secrets. I shall house the secrets of my order with reverence, and upon my death, shall become a repository for my successors.

Level 3 Feature:

Oath Spells.

Each oath has a list of associated spells. You gain access to these spells at the levels specified in the oath description. Once you gain access to an oath spell, you always have it prepared. Oath spells don't count against the number of spells you can prepare each day.
If you gain an oath spell that doesn't appear on the paladin spell list, the spell is nonetheless a paladin spell for you.

Channel Divinity: Astral Clarity.

You can use your Channel Divinity to heighten your awareness and draw from a well of lore and arcane knowledge. As a bonus action, you grant yourself a +5 bonus to Intelligence checks for the next 10 minutes. If an Intelligence check uses a skill with which you aren't proficient, you also add your proficiency bonus to the total of the check.

Channel Divinity: Otherworldly Mark.

You can use your Channel Divinity as a bonus action to mark a creature that you can see within 30 feet of you as otherworldly. In addition to its normal creature types, a marked creature is considered to have one of the following creature types of your choice for 1 minute: aberration, celestial, elemental, fey, fiend, or undead. The mark ends early if you mark another creature. When you use this Channel Divinity option, melee attacks made against the target are also made with advantage until the end of your next turn.

Level 7 Feature:

Aura of the Void.

Starting at 7th level, the touch of the Astral Plane graces you and your allies with easier travel and anonymity. You and friendly creatures within 10 feet of you ignore difficult terrain and can't be targeted by divination spells or perceived through magical scrying sensors. In addition, any hostile aberration, celestial, elemental, fey, fiend, or undead must spend 2 feet of movement for every 1 foot it moves within the aura.
At 18th level, the range of this aura increases to 30 feet.

Level 15 Feature:

Divine Reconsideration.

By 15th level, whenever you or another creature you can see within 30 feet of you rolls a d20, you can choose to roll a d20 and use either result (no action required). You can do so after the target makes its roll, but must decide before the GM determines the outcome of the roll. You can use this ability a number of times equal to your Charisma modifier, and you regain all expended uses of it when you finish a long rest.
In addition, immediately after you deal damage to a creature with your Divine Smite or a spell with "smite" in its name, you can mark that creature as if by your Otherworldly Mark Channel Divinity option.

Level 20 Feature:

Avatar of the Void.

At 20th level, you can transform into a harbinger of the void. You can use your action to gain the following benefits for 1 minute:
-You gain a flying speed equal to your walking speed and can hover.
-You gain truesight out to a range of 30 feet.
-Whenever a hostile creature within your Aura of the Void attempts to speak (such as casting a spell with a verbal component), it must first make a Wisdom saving throw against your spell save DC or be unable to speak until the start of its next turn, and any action used to do so is wasted. If the target is an aberration, celestial, elemental, fey, fiend, or undead, it makes this saving throw with disadvantage.
This effect ends early if you are incapacitated or die. Once you use this feature, you can't use it again until you finish a long rest.