Pact of the Great Flame

A Warlock draws their power from a force or entity that bestows their blessing upon them. Sometimes these beings are categorized by type, other by their ability. Your patron can only be described by their power: fire. Everburning, everbright, whether elemental or old god, they rule the domain of fire and place their spark within you to grow.

Expanded Spell List

You patron lets you choose from a larger list of spells when you're learning your warlock spells. The following spells are added to the Warlock spell list for you

Spell Level                             Spells
      1st                     Searing Smite, Burning Hands
      2nd                  Flame Blade, Aganazzar's Scorcher
      3rd                      Fireball, Protection from Energy
      4th                   Fire Shield, Conjure Minor Elemental
      5th                        Immolation, Flame Strike

Kindling Soul

When your pact if forged at 1st level, you become partially one with that which empowers you. You have resistance to fire damage, and you gain the ability to add fire damage equal to your Charisma modifier to all cantrips that deal fire damage. In addition, you learn the fire bolt cantrip and it does not count against the number of warlock cantrips you know.

Ashen Cloak

Starting at 6th level, your flesh begins to glow with the power of your patron.
As a reaction, when you are hit by a melee attack, you you can cause that creature to suffer fire damage equal to your Charisma modifier (minimum one)

Gift of the Arsonist

Beginning at 10th level, you can place a burning curse on a creature, causing it to feel you fire in every inch of it's body. As a bonus action, you point at a creature you can see within 60ft and curse it for one minute. The curse ends if the creature dies, you become unconscious, or if you end it as a bonus action. Until it ends, the creature cannot benefit from any feature that would grant it resistance to fire damage (including racial traits), and when  you deal damage to the creature, your attack deals 1d8 additional fire damage.

Ember Guardian

Starting at 14th level, your patron bestows you with a protector you can summon to your side.

As an action, you summon a fire elemental. It obeys your every command, and if not commanded to do anything, works to protect you as best it can. The elemental returns to the elemental plane of fire if you dismiss it as an action, or if it drops to 0 hit points. If you dismiss the elemental, you can resummon it, however any damage or status effects previously affecting it remain. When you take a long rest, the elemental also gains the benefit of a long rest. If the elemental drops to 0 hit points, you cannot resummon it until you have taken a long rest.
The elemental is statistically identical to a normal fire elemental, but it's attack modifier for it's touch attack is replaced by your spell attack modifier. The damage remains the same. In addition, the elemental has advantage when attacking any creature under the effects of your Gift of the Arsonist.