You can find the PoB / Gameplay at the end of the post

Concept/Playstyle:

We're using a total of three hexproof curses. One comes from the ascendancy and the other one from Whispers of Doom. Only one curse is self-casted, the other ones are automated in a CoC setup. Activation delay can be fully ignored because curse zones aren't affected by this. All damage gets converted to chaos damage using a Original Sin. This way we can take Wither and make use of Necromantic Conduit (Unholy Might) and Extraction for a lot of extra chaos damage. Most monsters don't have high chaos res and we don't need to invest in res pen. We also can take Event Horizon without its life-loss downside as we don't use a chaos skill. As we spend a lot of points in curse effects, there isn't much room for crit bonus, that's why we use Maligaro's Virtuosity. This sets our crit bonus to 300% and can't be increased or reduced. This way we can also take Pinpoint without its downside.

For clear, we want a skill with some crit chance (but also not too high, so CoC doesn't get triggered too often) that can hit many enemies. This is only to trigger CoC and explosions. I tried different skills (Arc, Spark, Fireball) and am currently sticking with Spark. But you can use whatever elemental skill you like (going ED/C DoT could also be a viable option, haven't tried). Sadly there's no good wand weapon skill (or only phys), this would help with mana. The actual clear damage isn't super high, this is for two reasons: First, we have a relatively low crit chance (a lot of crit chance comes from Malice). Secondly, all good damage multiplier gems are used for Flameblast. Cast curse for curse zone and spam Spark. Curse-wise you have two options here:

1. If you want more defence, take Temporal Chains as your main curse.

2. If you want more clear speed, use Despair as your main curse.

For single target/bosses we use Flameblast for a big boom (with the downside of a long cooldown). Crit chance gets capped by Pinpoint + Critical Weakness. Cast Curse + Sigil of Power -> Cast Spark to trigger CoC for more curses -> wait few seconds until Wither & Critical Weakness stacks are up -> cast Flameblast

Cons:

• definitely not the fastest mapper out there but also not super expensive to put together
• can only use CoC to triggers skills
• can't inflict any ailments
• Pinnacle bossing will be a bit of a pain because of the Flameblast cooldown (at least on max difficulty) and there's no way to get it to 0.
• You need to make sure you don't run out of mana and have energy shield. This can suck esp. on things with much DoTs that stop ES recovery like burning ground, ritual, King in the Mists or when you get body blocked.

Ascendancy:

Rupture the Soul > Dominion over Flesh > Necromantic Conduit

For the 4th notable you can either take Blackened Heart for more raw damage or Crystalline Phylactery for more QoL. I prefer Phylactery so I can get a lot of mana on kill, more evasion (+ higher ghost shrouds recovery) and some cooldown for Flameblast.

Eldritch Empowerment and Price of Power do nothing as Flameblast is a channeling skill.

We have three downsides that need to be covered:

1. 5% mana loss per second.

2. Unholy Might is only active while not on low mana (>35%).

3. 50% more mana cost if you have no energy shield.

Try to get as much mana + mana regen on your gear as possible.

Keep an eye on your mana pool and energy shield.

Mana will mostly be problematic at bosses. This is why we use a mana flask with % instant recovery, so you can get quickly above 35% when using Flameblast.

I'm currently searching for a way to fix this.

Defence:

Temporal Chains, Enfeeble, Hinder.

If you run Temporal Chains as your main curse, everything gets fkin slowed down.

Hybrid Life/ES/Evasion to avoid hits and be able to tank some (evade chance is somewhere between 50-75% depending on how much you invest).

Ghost Shrouds to recover energy shield.

Capped ele res and high chaos res.

Life on kill and 50% less freeze/shock/ignite duration so we can take anti-stun/slow charms.

Freeze or Blind on single target.

Gear:

• Wand: high Spell/Chaos Damage, Mana, +4 all spell skills, cast speed, high crit chance (dont' use %extra ele damage and %element dmg)
• Offhand - Omen Sceptre: Spirit, Mana, Int, mana reg, presence aoe
• Helmet: high ES, life, res
• Body Armour: high Eva/ES, life, res
• Gloves: Maligaro's Virtuosity with high crit chance
• Boots: high Eva/ES, life, movement speed, res
• Amulet: life or %life, mana or %mana, spell damage, cast speed, crit chance, +3 all spell skills - Anoint Mental Toughness
• Ring: Original Sin (make sure you buy one with 100% conversion as there are some corrupted ones with <100%)
• Ring: life, mana, mana reg, res, chaos damage, cast speed
• Belt: life, mana, res, charm slots
• Unique jewels: Prism of Belief +3 Flameblast, From Nothingwith Crimson Assault (if you use Phylactery), Megalomaniac (not necessary)
• Rare jewels: spell or chaos damage, curse magnitudes, crit chance or crit chance for spells, mana on kill

Try to get 2 sockets on helmet/gloves/boots and 3 on body armour (can also use gloves with 'debuffs have increased slow magnitude' corruption).

Make sure you get +levels to all spells, as we use different element skills and Sigil of Power and the curses also get levels.

You can of course also skip life on helmet/boots/body armour and get more energy shield instead (I prefer a decent life pool).

In weapon set 2 you use a Chiming staff with Level 18 Sigil of Power + Int. If you want to get the most out of Sigil, get one with +4 all spell skills and cast speed.

Megalomaniac (not necessary):

I'd only use one if it has at least two good stats.

When you search, you can also look for ones with Mental Toughness or Deep Trance and get another Anointment instead.

One of them (must-have) should be either Subterfudge Mask, Beastil Skin or High Alert.

Good 2nd/3rd nodes are: Distracting Presence, Roil, Ruin, Deadly Force, Chronomancy, Lasting Incantations, Prism Guard, Enhanced Barrier, Eldritch Will, Adverse Growth, Calibration, Profane Commander, Enveloping Presence, Arcane Intensity, Lingering Whispers, Spiral Into Sanity, Forthcoming, Fated End, Siphon, Touch The Arcane (some nodes like Volatile Catalyst, Crashing Wave or Mindful Awareness sadly aren't available)

Runes:

• Helmet: 2x AoE
• Gloves: 2x Curse Magnitudes
• Boots: 2x Cooldown (or presence aoe / chaos res / %life / %mana if you don't invest in cooldown)
• Body Armour: Iron runes (or chaos res / %life / %mana)
• Wand: crit chance
• Sceptre: Presence AoE

Requirements:

• Attributes: 205 int for Lv 20 gems, 54 str for a Lv 18 Malice Omen Sceptre, 73 dex for gloves/gear
• Body armours maybe have a higher dex requirement than gloves. You can also look for one with reduced attribute requirements.
• If you need more attributes, you can respec the small spell damage nodes right at the witch start and take the attributes nodes instead.
• Spirit: min. 235 (or drop Mysticysm, Cannibalsm or Strong Hearted)
• If you reach 255, you additionally can use Vitality.
• Levels and high mana pool + mana regen.

Gem Information/Options:

If you want more AoE on Flameblast, you can replace Concentrated Effect with Fire Mastery but you need to stay close to the enemy anyway as Flameblast casts around you and for the enemy to be in presence range (or use Fire Mastery instead of Deliberation and Deliberation for your clear skill). Ingenuity doesn't lower the cooldown by much, don't use it. Excise/Hourglass don't work with Flameblast.

If you want to lower mana cost for the main curse, replace Magnified Effect with Chaos Mastery. You can use Magnified Effect for Sigil of Power instead.

CoC-Setup:

Use the lowest possible level curses because of mana cost (curse level mostly scales duration and AoE but cost a ton of mana).

For the 5th and 6th slot, you have the following options:

• If you want a powerpoint show, use Expanse + Spell Cascade for absolute curse escalation (Expanse doesn't add a cooldown)
• Essence Drain Lv 3 + Blind for more evade chance
• Essence Drain (max Lv) + Chaotic Freeze^7 for freeze ability and additional damage

I prefer Essence Drain + Blind. This increases the maximum energy needed for CoC (so it triggers less often and doesn't drain your mana so fast).

Auras are: Malice, Cast on Critical, Withering Presence and Ghost Dance. On Weapon Set 2, you only activate Withering Presence and Ghost Dance.

Bind Flameblast, Spark and Curse only to Weapon Set 1, so you instantly swap back after using Sigil of Power.

Also:

• Don't use Decaying Hex or Impending Doom, the damage falls off in late game. It also locks you out of Ambush.
• DO NOT USE VOLATILITY

Skill Tree:

The reason we don't invest much into cast speed is simply because of the mana cost. Cast speed also increases Flameblast mana cost. So we just get some cast speed on the wand on amulet to not feel clunky.

For more AoE, you can take the Roil cluster. Or vice versa take Ruin cluster for more damage and less AoE.

Can also consider taking Eternal Youth or ES recharge/recovery nodes.

As mentioned above, you can also go for full damage with Blackened Heart and play without From Nothing and Megalomaniac jewels. Use rare jewels instead. Good anoints for max mana increase (for Blackened Heart) are either Calibration or Eldrtich Will. For more damage, take Ruin (3 points). This way, you can get up to 4.5 mil damage. (But as most bosses still won't be one shot even with that amount of damage, I decided to invest more into cooldown and defence instead)

Calculations/Config:

Information about PoB custom mods/config:

• 750% more damage = Flameblast stages (75% more per stage)
• 20% more damage = Deliberation
• The remaining mods are from the socketed jewel in the Phylactery.
• I set the Sigil stages to 2. This is pretty much always the case at bosses.
• Maligaro's Virtuosity seems to be currently bugged. It shows 400% crit multi but it's actually 300%, so full damage is a bit lower.

Cooldown:

22% in jewel radius, 10% from boots, 10% from Megalomaniac. This brings us down from 15 to 10,5 sec (or 11,5 without Megalomaniac). If you add Ingenuity to Flameblast, this will reduce the cooldown roughly by 2 secs, so not worth it imo.

Note that it's cooldown recovery RATE, meaning it's not a flat reduction. If you have 100% CDR this will halve the cooldown time.

Presence radius:

Base = 4 m + 85% from sceptre = ~ 7,5 m

Skill Duration:

We get 60% skill effect duration from tree passives (or 45% without Megalomaniac).

• Malice: 5 sec. base duration x 1,6 = 8 sec. / 0,53 (inflict rate) = 15 stacks
• Wither: 7 sec. base duration x 1,6 x 1,4 (Persistence) = 15,68 sec. / 1,42 (inflict rate) = max. stacks
• Also, Temporal Chains makes debuffs expire slower, so we reach max. wither and crit cap easily.

Additional Information/Tips:

• Avoid maps with the following mods: burning ground, reduced cooldown recovery
• Charges don't add much (I tried Sniper's Mark / Charge Infusion / Resonance) but they don't add much. Even with Sniper's Mark you don't get over 300% bonus (it also has high dex requirement).
• Maybe need to play around with how much crit weakness stacks / crit chance you actually need on gear to get capped. I have a total of 175% on gear + jewel and get capped with 16 stacks.

PoB:

Note: Doesn't show the full dps as I can't set Flameblast stages.

https://pobb.in/A_Kl8hN1_fFm

Gameplay:

T18 Harambe (almost oneshot)

T16 Doryani (Stone Citadel)

T16 Napuatzi

T15 Steppe alch&go with current setup (Spark + Despair)

This was a T15 Savannah with Fireball + Temporal Chains

(the Fireball setup wasn't very good. It has good base damage and can hit multiple targets with the explosion and firebolts but also has longer cast time, higher mana cost and high rng with the extra proj/wildshards. It would need some invest in extra proj.