Patron of Riddles

Holding the knowledge of eternities, a sphinx can bestow this gift onto mortals who prove themselves worthy. 

Whether you sought a sphinx to test your knowledge and wits, or you stumbled upon one by chance, you have bested the sphinx at their own game, and have been rewarded for your wit.

The sphinx has granted you a special knowledge. A knowledge to answer questions before they are asked. You can see when an enemy will draw their blade or utter a curse, mere moments before they strike. But your blade is faster. Your incantations more rapid. You know their question, and you will give them your answer.

The sphinx rarely ask for more from their pact holders beyond knowledge. The sphinx will occasionally attempt to enter your mind to speak with you, or control you, in an attempt to gather more knowledge, riddles, or jokes. 

As part of your pact you should oblige your patrons whims...lest they play with your mind instead.

An Answer

Starting at first level you gain an additional reaction at the start of each of your turns. 

Additionally when a creature provokes an opportunity attack from you, or you are granted an attack via reaction from another source, you may use the Eldritch Blast cantrip in place of a melee attack.

Greetings Traveler

You gain a 3rd reaction at the start of each of your turns. 

In addition, when you make an opportunity attack, or are granted an attack that uses your reaction, you may attack or cast the Eldritch Blast cantrip twice as part of the reaction. The attack or spell must target the same enemy.

Incorrect Choice

Gain a 4th reaction at the start of each of your turns. 

In addition gain the Sentinel feat starting at 10th level. 

When using your reaction to cast a spell or make an attack you may spend a spell slot to give yourself advantage on the attack roll or impose disadvantage on any saving throws a target of a spell would make.

Sentinel

Your foes think they are wise, but you are wiser. When an enemy attempts to move past you you stop them in their tracks. When they move to harm your ally,  you have your own response.

You gain the Sentinel feat at 10th level. 

Deny Passage

You reach into the aether as a creature attempts to teleport and deny them their plans

As a reaction if a creature within 10 feet of you chooses, or is forced to, teleport or change their current plane you can deny the movement. The creature disappears for a moment, then reappears within 5 feet of their previous location.

In addition as a bonus action on your turn you may grant one ally within 30 feet that can see or hear you one of your additional reactions until your next turn.