The Frost Fire Royal

By some means you've managed to make a warlock pact not with some eldritch entity in your world, but with an actual person in the real world, by name of FrostFireRoyal. How did you do this? 

Expanded Spell List

The Fiend 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.

Fiend Expanded Spells

Spell Level	Spells
1st	shield, burning hands
2nd	aid, scorching ray
3rd	fireball, sleet storm
4th	conjure minor elementals, wall of fire
5th	flame strike, cone of cold

Frozen Flame And Burning Ice

Starting at 1st level, your power from the most contradictory individual in existence provides some benefits. You have resistance to either fire or cold damage, you choose at the end of a long rest, and whenever you deal damage of the opposite type, you can use your reaction to convert it into your currently selected type. 

Cold

You have chosen cold damage 

Fire

You gave chosen fire damage.

Paradoxical Potency

Starting at 6th level, you can call on your patron to bolster magic in your favor. As a bonus action, you may roll a d6, and add the rolled number to the damage roll of the next spell you cast before the end of your next turn. You also gain a number of temporary HP equal to half the number rolled, minimum of 1. 

You may use this feature a number of times equal to your proficiency bonus per long rest. 

Power in Change

Starting at 10th level, when you use your Frozen Flame and Burning Ice reaction, you ignore resistance and you may deal additional damage equal to your charisma modifier.

Subjection to Torment

Starting at 14th level, when you hit a creature with a melee or spell attack, you can use this feature to instantly transport the target through the planes. The creature disappears and is teleported before your patron, who lectures them about some obscure concept. 

At the start of your next turn, the creature reappears in an unoccupied space within 10ft of where it disappeared, and must make an intelligence saving throw using your spell save DC or become stunned for one minute. The creature may repeat the saving throw at the end of each of it's turns, ending it on a success.