The Silver Flame

This subclass allows you to have Tanwen X'ek of the Silver Flame as your patron. He will grant you access to The Eternal Silver Flame in exchange for his control over your actions in some scenarios. This Subclass allows you to visit Tanwen in order to learn from him and to heed his orders, even if the process may be tiring at times. Additionally, your access to the eternal flame means your pyromancy is greatly enhanced and as such you become a formidable attacker in the front line, but it also allows you to form a bond between your allies - augmenting their attacks to deal even more damage and healing them when you destroy a foe. Despite all this granted power, Tanwen X'ek is an unpredictable being - and as such your ties with him may force you into situations where you have to commit to actions you may regret. As the saying goes, "with great power, comes great responsibility".

Patron Conclave

From 1st level, during a long rest, you can choose to visit Tanwen X'ek as an illusionary figure in his prison-like plane. In this meeting you regain all uses of abilities specified to recharge in this way, and you are able to speak with Tanwen and learn from him. Because of this, you are granted expertise in one skill type after learning from X'ek. Every conclave you are able to swap this knowledge for expertise in another skill. Additionally, Tanwen may present you with tasks to complete and may reward you if such tasks are completed by the next conclave. Finally, you may present a weapon to Tanwen X'ek. This weapon has it's damage type changed to fire until another weapon is presented and it is also silvered.
When you leave the conclave, you must roll a d20. Meeting such a powerful being can be overwhelming, and as such upon a 1 you awaken with 1 level of exhaustion after the long rest.

When you swap your expertise, return to the character builder and select a different expertise option.

Silver Flare

At 1st level, you have been gifted the ability to borrow from The Silver Flame, the eternal source of Tanwen X'ek's power. Five times per conclave, you can add a d6 fire damage to an attack which successfully dealt fire damage to an enemy. You roll a number of d6 equal to the spell slot level of your current pact magic spell slot(s). The burning flames of your pyromancy flash white as you inject the eternal Silver Flame.
Alongside this, the call of the Silver Flame has made your 'Eldritch Blast ' now deal fire damage.
You regain all uses of your Silver Flare after a conclave with Tanwen X'ek during a long rest.

Spread his Influence

At 6th level, your frequent discussions with Tanwen X'ek have helped you to learn how he has managed to capture the hearts and minds of so many, despite his possession of such an innate ability for destruction. You can now take advantage of this infectious connection, allowing you to - after a long rest - place your 'Silver Mark' on a number of creatures equal to your proficiency bonus within a 60ft range. Whilst a creature is marked, you gain advantage on ability checks made to maintain spell concentration and you are able to cast spells even when under the influence of a condition which would normally prevent you from doing so (restrained, anti-magic sphere, raging etc) unless you are incapacitated or unconscious. The effectiveness of this ability is up to your DM's discretion. In addition, whenever you make a successful attack against a creature and deal fire damage to it, you and all marked creatures can gain 1d4 + your Warlock spellcasting modifier in hit points, and you also all have resistance to fire damage.

At 10th level the healing effect increases to 2d4,  at 14th level it increases to 3d4 and the fire resistance is replaced with immunity.

Resistance

At 6th level, you and all creatures affected by your Silver Mark are resistant to fire damage.

Focused Mind

At 10th level, you have been a puppet for Tanwen X'ek for some time now, and as such you have become a conduit for his influence. You can now telepathically communicate with people who are affected by your Silver Mark and are within 120ft. Additionally, you can use your reaction to change a marked allies' attack to fire damage, and as a part of this reaction you can use a 'Silver Flare' to add your additional fire damage to the attack. You can also use your bonus action to swap your position with a marked creature, then gain a 1d4 bonus to your AC for 2 rounds if a hostile creature is within 5 ft of you.

Finally, when you more than 20 fire damage to a creature in a single attack you can force them to make a dexterity saving throw against your spell save DC. Upon a fail, they are on fire. Creatures which are on fire have disadvantage attacking any creature other than yourself.

Molten Forge

At 14th level, your power has grown strong enough that you share a fraction of your Patron's near infinite wisdom, and as such you know the DC of all ability checks you make before you roll, and you know the AC of any creature which is on fire. Additionally, You have a 'Forge pool ' of 30 points which you can borrow from to add to your attack rolls and ability checks. Example: if you rolled a 14 on an attack roll which against a creature with an AC of 19, you can use 5 points to bring it up to a 19 and succeed the check. Additionally, you can expend 10 Forge pool charges to regain one 'Silver Flare' and, once per conclave, you can touch a creature and heal them for the remaining amount of charges left in your forge pool. Fully expending the pool in the process. Your pool resets after a Conclave with Tanwen X'ek, however you will need to forfeit your skill expertise to do so.