The idea from this build came about from like two other builds i played. i wanted to initially do a Fire based pyromaniac for a character but could never get it it to work until now. Feel free to edit what you like and improve upon what you think could be better. I've done quite a lot of testing and this is the version of the build that works best for me so its far from perfect or what you might want out of a build.
With that out of the way lets get into the few caveats to this build shall we.
Things to Note
1.This build has very good clear if u keep it going.
2.It has infinite ramp up with Flaming Hell's and the Instant Combustion Rune
3.Good Mana sustain provided you keep close to enemies.
4.Even though it has low health, you tank off of your Mana pool, and Gain a shield based off of it as well.
4.It has max resistances, 100% Overpower and 81% Damage Reduction
5.Low health and kinda squishy,But Large Shield based off your Mana so most things wont even touch your health.
6. If you use this i would advise turning down the audio and sound effects because the constant Firestorm spam does get annoying on the ears.
8. The highest i have gotten on the endless Random Anomaly's with this build is Mythic XV Tier 700 odd,It was still fine in terms of damage and survivability so it shouldn't hurt even if you push further.
9. It should be worth saying that i do not have a maxed Pet from the DLC yet but I'm sure the artifacts could take this build further. I have a lesser Beast so i can show what runes i using up until there.(When i get a greater beast i will update the guide)

How do we stay alive?
Most of this builds defence comes from our large shield granted by Vestige of Lost Souls,max resists,high damage reduction values.

It also uses the passive boon from Ritual of Souls for the health,damage and mana. (With all our mastery and the nodes from the DLC we get a 10% Boost to our stats for each soul, we also have a max soul cap of 19.)


While also using the Lich Power Ultimate to increase our evasion,and some more damage reduction.With our cap of 19 souls and a generally good sustain for the souls so Frozen Veil works well for some more damage mitigation.


Wheres our damage come from?
As mentioned earlier we use the Sun & Moon set to boost most of our damage. However most of our DPS will come straight from Firestorm and In turn it stacking Flaming Hells.



We use Flaming Hells in conjunction with Detonation and the Instant Combustion rune.



This allows us to quickly ramp stacks of Flaming Hells on an enemy then detonating it, But we are using Sun & Moon so our mandatory frost skill of choice is Frozen Fate.


This Becomes Important later but i will explain more when we get there. We will also be using Life Reap for the weakening passive but you can use the other options here so just choose whatever works best for you.


More often then not i found myself Spamming my Binds for Frozen Fate and Firestorm and rarely using Detonation as mostly everything dies before you get a chance to cast it.Generally I leave detonation for the bosses.
This Pretty much summarises the damage dealing skills.

Now what about Movement?
As far as grouping and movement goes we will be using soul warp as our main movement skill.our hotbar is already pretty full so we just invest in the ability in the skill tree then use a scroll to cast the spell. (in this case the scroll might be a better option over the codex so u can spam it)

As for grouping enemies ive found the option to be Lightning Wryms.

Now the build is pretty tight on points in terms of what goes where in the skill trees but as always there should be wiggle room to invest in what you want.So for the Corruptor tree, we spend a whopping total of 0 points in the corrupter tree so no image for that one.

The Lich Tree

This ones pretty simple, at first we grab both passives for some Mana and Critical hit damage.Next you want to grab Soul Warp and all its passives because even though we don't have the skill on the hotbar we can still benefit from the passives.now heres where it gets a little weird.We put one point in Bonechill and then max out the rest of its passives along the tree. Remember our frost tree is mainly so we can activate Sun & Moon and get the Lich Power ultimate.Next we grab frozen veil and max it,you will also want to put one point in Deaths Breath so you can dump 2 into Spirit of Torment.

We will also max out Frozen Core for the cooldown reduction.Now we also take Frozen Fate as our active skill for Sun & Moon. (Keep in mind soul warp can also trigger this effect) The other main Reason we get Frozen Fate is because of the Frozen Graves rune.

This allows us to cast it in conjunction with Firestorm and Detonation to pretty much insta kill enemies. As far as its passives go its up to you,however i like using Brittle Bones to help boost the damage a little. And Lastly we Grab the Lich Power ultimate Skill. Make sure to also grab Corpse Combustion.


The Demonologist Tree

Here we grab both passives again for the health and damage reduction. We then max out the entire Flaming Hells passive and all its linked passives.We put 1 point into Detonation because of the rune its more of an activation switch.We then max Demon skin's passive Demonic Fury for more AOE.

Next We max both Soul Empowerment and Demonic Appetite for the passive boosts.


Lastly we spend a single point in Firestorm

It would be more but we needed its passives for the rest of the build, and we were stretched thin in terms of points.so Put one point in each passive and lets move on.

Hell Caller will act as a form of our soul sustain as we will pretty much always be spam casting firestorm this is very handy.Next we get Armageddon

This combined with Crown of Innate probability will allow us to spam cast Firestorm without worrying about cooldowns.


The Reaper Tree
Our points in this tree will go mainly to Ritual of Souls and the all the different passives, including Sudden Death and Masochism.



We Start with the passives,Max all of Masochism's passives for the boosts it gives.You then want to put one point into Life reap and each of its passives for the soul gain and some extra damage boost.We then max Ritual of souls as well as one of Undeaths passives for the Mana/Health restore.



Now On To Mastery
So the Mastery Leveling progress is a little weird but ill try break it down as best i can.
The First 26 Points you want to drop invest are to grab the Cooldown reduction and Ritual boosts.

Next you want to Put 51 Points into the Three main trees of this build.
Prioritise Demonologist,Lich then Reaper In that order.



Next put 51 points in the Corruptor tree for the Ritual perk at the end.

Next Put 26 Points each into Class Mastery II and III. You can Choose which one you go for first.


Next we want 65 points total in each class mastery for the Bane skill Perk. It should look something like this.We have only five points in the resistance passive because with our gear that's all we need to cap them in mythic 15+ dungeons. (This is with DLC Passives)

and lastly at Mastery 600 my tree Looked something like this:

From here keep dumping points into Mana.

*Note*
I Highly recommend leveling the warlock to 100 beforehand then trying this build,as most of the things needed to make the build work are true legendaries or runes you can only get through the endgame dungeon Anomaly's. If you have already unlocked Tinka's domain and want to level a character quickly i recommend farming or gambling for a Chronicle Of Knowledge,Turning it into a rune and applying it to the Heart Of the Community starter accessory.


I would also suggest maxing out the experience gain through the greater augment enchanter in Tinka's Domain and rolling for experience gain on most of your items. Then Just repeat run normal Dungeon Anomaly's and increase the games default difficulty and the Anomaly difficulty as you level up.

So This build revolves around using the infinite scale bonus off of the Regalia Of Burning Hell's Set.

I've tried numerous item/rune combinations and this is what turned out the best for me,or at least what i enjoy playing the most. A few things to note:We mainly just want the 3 piece set bonus to stack up Flaming Hell as fast as possible. I will be going over each piece of the set individually and why we use it, then ill go over the runes/enchantments and gems.

The Helm
Now usually i would say go for the set bonus and use all four pieces but today instead of doing that and using the Burning Hell Crown.

We Will be using the Crown of Innate Probability instead.This Gives us a 100% Proc rate on all of our skills and passives including Armageddon,

this in turn allows us to not only spam cast Frozen Fate and Firestorm, but it also lets all our other passives stack and work faster.


Armour
For our armour and pretty much the rest of our normal pieces we will be using the Regalia Of Burning Hells set. So this Means For the Robes we use Burning Hell Robes


Boots
For These we use Battle boots

Pretty Useful cause we will always be spamming soul warp.

Staff (Mainhand)
For this we will be using Burning Hell Scepter.

It is Important to note that for this build to work as well as it does you will need to craft it into its mythic variant so you can unlock two rune Slots.To do this simply collect x10 of each Greater Boss Anomaly's Parts as well as the two mythic weapon parts. Visit the Hellforge and Transmute all of these parts along with the Scepter to create a mythic version of it. In order to access the Hellforge you require the DLC and to have spoken to Diana Jones after finding a mythic weapon part. Any of the boss drops apply to every class but the mythic parts you need are class specific so you will be required to run the Greater Boss Anomaly's on the Warlock to create a Mythic Version of this Scepter.

Spell Tome (Offhand)
Here we will be using the last of the set pieces for this set,The Burning Hell Opus.This completes our three piece set bonus.

Not much else of importance to note here so lets move on.

Amulet
The Amulet we use is the first part of the Sun & Moon set.Can You Guess what its called? Yep its moon.

The main reason we use this set is for its very high elemental damage bonuses to both frost and fire damage.The one we will be using it for is of course fire.Through the gems and some elemental damage bonuses i was able to stack the fire damage bonus up to around 1890%(Please note I have around almost 3K in my mastery at the time of writing this guide and the damage bonus from Sun & Moon is around 2300% currently so it will scale up along with your frost and fire damage as you invest more into the mastery tree)


Ring
For the ring we use the second piece of the set, Sun. Theres not much else to note here.


Accessory
For this we use Cosmic Cape.

Our main source of damage comes from stacking our Mana and then converting said Mana to damage.with the full build we have around 220k mana without the cape. Just by equipping the cape we bring our damage up from a baseline of around 40k all the way to 1.8 Million (with all our souls).

Something to note this build uses four greater runes so we have a rune of greatness slotted on our amulet to bring the cap to 4.We also convert several legendary's and True Legendary's into crafted runes.Also feel free to edit any of the rune options if you feel like theres a better choice, as ive stated before its my first build and guide so not everything's bound to be perfect.

Helm Rune
Here we use Life Guard for the damage reduction.


Armour Rune
Here we use Vestige of Lost Souls for the passive Shield it grants.

By Investing heavily into Mana we not only increase our Damage but also our shield which will in turn keep us alive for longer.

Boots Rune
The rune on we use here is Frozen Graves.

It is also the reason we chose Frozen Fate Over any of the other frost skills. Ive found this rune to be a big help clear wise as anything not killed by Sudden Death dies to this or Detonation setting off all the Flaming Hell and Combustion ticks instead.

Staff Runes
So remember we want to have a Mythic version of the Scepter instead of a normal version so we can slot two runes instead of just one.The runes of choice are Boomstick For the extra Combustion damage depending on how many Flaming Hells stacks there are and how much time is left on them.

& A lesser rune of Total Armageddon for the 100% Cooldown reset.This combined with Crown of Innate Probability means Firestorm is almost always off cooldown and allows us to spam it, and keep its stacks up.


SpellTome Rune
For this one we use Jon's Book Of Souls to increase our soul cap by 10 bringing us to a maximum of 15 souls.(19 with the dlc)

This is very nice to have because it increase the effect of Masochism and Ritual of Souls. This will in turn boost our Damage/Health/Mana as well as our Mana and Health regen. This is also very good cause it increases the amount of shield provided by Frozen Veil, and Vestige of Lost Souls

Amulet Rune
Here we go plain and simple and just use a Lesser rune of Greatness to up the Greater Rune cap by 1.


Ring Rune
For the rune here we use ring of pure energies.

The Mana Bolster is very nice so its indirectly contributing to most of our damage.You can try alternatives here if you so wish.Its worth mentioning that i did try jeopardy here instead but firestorm doesn't proc it fast enough to maintain the bonus and with Ring of Pure Energies slotted i was doing more damage anyway.

Accessory Rune
In this slot we have another rune that acts as a key piece towards the build. The rune of Instant Combustion.

not much else to say here other then it makes things go boom.

So the enchanting for this build is a little strange. We want to generally go for resistances, damage reduction and a few fire boosting enchants. The Below images are just of the enchants you should have but most are optional. The resistances are required to hit cap but feel free to play around with everything else.

Helm Enchants


Armour Enchants


Boot Enchants


Staff Enchants


Spell Tome Enchants


Amulet enchants


Ring Enchants


Accessory Enchants

So For gems we roll cube sockets on everything except our Weapon and Off Hand,on them we roll hexagon slots. we will mainly be stacking Mana, and then Fire damage and Burn(Fire on hit)

Helm Gems

3x Polished Cube Kyanite

Armour Gems

4x Polished Cube Kyanite

Boot Gems

2x Polished Cube Kyanite

Staff Gems

2x Polished Star Citrine

Spell Tome Gems

2x Polished Star Citrine

Amulet Gems

3x Polished Cube Citrine

Ring Gems

2x Polished Cube Citrine

Accessory Gems

2x Polished Cube Citrine

So as mentioned earlier i do have the dlc and have finished and unlocked all the nodes. They do add a lot,but the build works just fine without it. Id recommend upgrading the Southern Scorched Lands Tree first for the fire Buffs then the Frozen North tree. Again its optional so upgrade and unlock the nodes if you would like.

Beast and Artifacts
For the First two artifacts you can use whatever you like but im using these two


For the next two i use these

So now you've gotten everything built and are wondering how this all works.Lets start By looking at the hot bar.

At first it may look a little funny but allow me to explain.

LMB-Detonation.
LMB-Life Reap
LMB-Lich Power
1-Firestorm
1-Frozen Fate
4-Ritual of Souls
RMB-Soul Warp
3-Lightning Wryms

So above is what your bindings should look like.We have Detonation, Life Reap and Lich power Bound to LMB as we only need to cast them every so often or while in large groups of enemies. You can swap LMB for 1 if your more comfortable with that. it'll just mean swapping the button you use to cast the grouped abilities. Frozen Fate and Firestorm are bound 1 as these will be our main form of damage output and Firestorm needs to constantly be cast in order to maintain 5 stacks. I Use RMB as my movement button so i bound soul warp to it,Feel free to change it if u want.Lightning Wryms is bound to 3. Lastly Ritual of Souls is Bound to 4, it doesn't really need a binding it just needs to exist on your hotbar to grant the benefits. i have it on 4 for more of an emergency oh no button when i'm in a tight spot.

Spell Cast order and general use
So the main way you want to play this is by casting firestorm and frozen fate a few times before warping into a group of enemies. After warping into the mob cast Lightning Wryms to pull everything towards you, Keep casting Firestorm (Remember you want to keep the stacks up) Things should drop to lowish health before instantly dying, If they don't you cast detonation and life reap to finish the job.

Things of importance
1.You should always be warping with Soul warp and casting Lightning Wryms alongside Firestorm/Frozen Fate.
2.Gaining souls will give you a pretty decent barrier/shield. I've found it almost never breaks if you keep moving.
3.You should always be at full Souls 19/19, If you do have Ritual of souls bound use it whenever your shield from Frozen Veil and Vestige of Lost Souls Breaks.For the extra security you could also cast Healing Touch when you do this as well.
4.For bosses avoid their attacks and keep Firestorm's Stacks up, wait until they reach high enough stacks then use Detonation and life Reap. (The stacks from Flaming Hells do not expire or vanish when you cast Detonation so you can spam Detonation if you like.)
5.Sitting still will get you killed, this build relies heavily on the fact that you are always moving so keep that in mind.

How to rebind the hotbar?
1.Pause the game and go to settings
2.Go to controls

3.Select create new Profile

4.Click Player one keybinds.

5.Scroll down till you see these.

6.From here just click the X to unbind the slots you want, Then click on the unbound Slot and it will prompt you to click whatever key you want to now bind to the slot.
7.And just like that You've rebound your keys.

Thanks for reading my very jank and crappy guide.If you made it this far thanks i hope you enjoy the build as much as i did. lastly id like to take a moment to say all of this is going off of what i have experienced or done in the game so its no where near perfect, there's bound to be some flaws and ways to do things better. Feel free to give feedback and ideas/suggestions i'm open to everything. Have Fun