The Forbidden

You’ve made a pact to find forbidden knowledge and secrets and in return you will receive the same.
Whatever may be giving you power it's hunger for learning new information will never be fully sated.
The source of your pact would be immortal beings, a powerful spellcaster, a sentient item or something you can work with your DM to create.

Expanded Spell List

The Forbidden 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.

Forbidden Expanded Spells

Knowledge is Power

At 1st level, you gain the ability to tap into stolen knowledge. You have a pool of d6s that you spend to fuel this ability. The number of dice in the pool equals 1 + your warlock level.

When you deal damage to a hostile creature, you can spend dice from this pool. You may use the dice pool to either:

1) Deal additional damage by 1d6 times the amount of dice expended from the pool + charisma modifier.

2) Heal yourself 1d6 times the amount of dice expended from the pool + charisma modifier HP.

The maximum number of dice you can spend at once equals your charisma modifier (minimum of one die).

Your pool regains all expended dice when you finish a long rest.

Own Thoughts

Starting at 6th level, you have learnt how to defend against outside influence. Your intelligence score increases by 1 and you gain proficiency to INT saving throws.

Stolen Secrets

At 10th level, your peering into minds has given you knowledge to use your magic to predict incoming attacks.

You may use your reaction when you or an ally takes damage from an attack within 60ft centred on yourself. 
You may expend dice within the dice pool of the Knowledge is Power feature to reduced the damage taken to a maximum of 0, any further damage reduction is lost.
The maximum number of dice you can spend at once equals your Charisma modifier (minimum of one die).

Beyond the Veil

At 14th level, you gain the ability to magically steal the spell energy from another spellcaster.

After a creature casts a spell that is within 60ft, you can use your reaction to force the creature to make a saving throw with its spellcasting ability modifier. On failure, you negate the spell’s effect, and you steal the spell's energy. The spell energy restores Knowledge is Power dice pool or an equivalent spell slot up to level 5.

You can use this feature an amount of times equal to your charisma modifier. 

You regain all uses after you finish a long rest.