Quick Jump

• Pros & Cons

• Skill Tree 

• Gems Setup

• Gear Setup

• Leveling Gems Setup

• Mechanics

Pros & Cons

Pros

• + decent AOE
• + great single target damage without Barrage or Elemental Hit
• + great clear speed with usual high Pathfinder mobility
• + permanent flask uptime
• + no need to PIERCE heavily, like in CA setup
• + REFLECT IMMUNE (all reflect!)
• + 45-65% dodge

Cons

• - Still pretty squishy as relies mostly on acrobatics and Evasion.
• - stacking Virulence is harder with slow bow
• - 111 INT required for proper gearing

About Mechanic

In fact, understanding how a build works can really help us achieve it better. But I know that some players may just want to quickly browse what they want, so I will take this part in section 'mechanics' last

Skill Tree 

Ascendancy

Nature's Reprisal -> Master Toxicist -> Nature's Adrenaline -> Nature's Boon

Bandits

Kill All

Pantheons

The Pantheon List

• Major: Lunaris
• Minor: Gruthkul

Passive Tree

Leveling Gems Setup 

Start with Caustic Arrow + Pierce and use it till level 12 when you get Toxic Rain. 

• Toxic Rain 3L: Toxic Rain-Mirage Archer-Void Manipulation
• Toxic Rain 4L: Toxic Rain-Mirage Archer-Void Manipulation-Vicious Projectiles

In act 2 you will get Herald of Agony after doing Sharp and Cruel. Just buy minion damage gem and you are set.

Herald of Agony 4L: Herald of Agony-Vicious Projectiles-Minion Damage-Faster Attacks/Withering Touch/Damage on Full Life

At Level 24 get Despair and at level 31 start using it with Blasphemy. You will drop it later when you get Witchfire Brew.

Endgame Gems Setup

For Uber Lab enchant

40% Toxic Rain damage if not running 6L Herald or using Coming Calamity. 30% Reduced Herald of Agony if running 6L Herald on Belly of the Beast and everything else.
Link setup here is a balance between dot, poison and pod explosions!

• Toxic Rain 5L: Toxic Rain-Damage on Full Life-Void Manipulation-Vicious Projectiles-Mirage Archer
• Toxic Rain 6L: Toxic Rain-Damage on Full Life-Void Manipulation-Vicious Projectiles-mirage Archer-Added Chaos

For maximum DoT stacking

Toxic Rain 6L: Toxic Rain-Void Manipulation-Vicious Projectiles-Swift Affliction-Increased Duration-Efficacy

• Herald of Agony 5L: Herald of Agony-Vicious Projectiles-Minion Damage-Withering Touch-Damage on Full Life
• Herald of Agony 6L: Herald of Agony-Vicious Projectiles-Minion Damage-Withering Touch-Damage on Full Life-Maim.

Gear

For Leveling

Silverbranch is great till you get Quill Rain or Death's Harp.

Use Lochtonial Caress till level 50, when you can switch to The Embalmer

Belt: https://pathofexile.gamepedia.com/Wurm%27s_Molt helps a lot to leech some mana!

Any life/resists quiver till you can afford https://pathofexile.gamepedia.com/Drillneck

Pretty much any quiver can be used: List of unique quivers

Chests are 6 options

• Cherrubim's Maleficence generic: best for overall damage
• Belly of the Beast: for high life/resists (7+k life)
• The Coming Calamity: BEST for Crawler + the only way to use Grace as an aura on a 6L Herald. But it would be very hard to get proper socket colors as you need 2R3G1B! Here also recommend Phys to Lightning or Minion Speed as a second blue skill gem.
• Kaom's Heart: the only way to reach 8K life! You will have to put Crawler in helm or gloves
• Loreweave: another good all-around for both damage and toughness.
• Carcass Jack is not bad, but would be not so easy to get 2R3G1B there.

Gloves: The Embalmer

Boots: any rare HP/res or Atziri's Step

Rings: Steel Rings or anything with Chaos Damage and Chaos Damage to Attacks

Amulet: Impresence with Chaos Damage or any High Life/Resists.

Helm: Starkonja or any rare. In case of Kaom's you need Shaper helm with Minion Damage/Conc.Effect

Jewels: 1 Spreading Rot

Belt: Stygian Vise high hp/res and CHAOS DAMAGE + Damage with Ailments. This one is crafted with Aberrant Fossil.

Bows: Lioneye's Glare/High Phys rare.

Quivers: Maloney's Nightfall is a great cheap option, Drillneck or any rare phys/hp/res. Drillneck is here for flat phys and attack speed. It does not pierce. For Maloney you might need either Blind Support or high Blind chance on jewels. Will work with Smoke Cloud, but not as reliable. 

Flasks:

• Witchfire Brew (if you don't have Impresence)
• Coralito's Signature
• Sulphur/Quicksilver with anti-freeze
• Blood of the Karui / Any Life Flask with anti-bleed
• Atziri's Promise for LEECH

FOR THE RICH GUYS

Crazy +1 arrow quivers. Corrupted Gear. GG Steel Rings with Chaos Damage

Mechanics

TOXIC RAIN

First of all it's a classic attack bow skill which directly scales with WEAPON DAMAGE. At the same time the skill itself has 3 phases:

• actual arrow hit
• pod damage over time / move speed debuff
• pod explosion

The first one is pretty normal. Like any attack hit. It's pretty low damage since it's only 50-72.8 of base damage

The second one lasts 1 second by default and does CHAOS damage over time. 

It's also pretty small and is around 15% of what caustic arrow does. HOWEVER! , it can be scaled with Increased Duration and Skill Effect Duration, as well as Concentrated Effect and a lot of different gems like Swift Affliction and Efficacy. You will need about 1.5-2 APS (for 7 Pods on the ground) to start reaching the numbers of the CA. Nature's Reprisal pathfinder ascendancy also increases the AOE of pod DoTs and explosions. The amount of attack speed and longer duration of pods greatly increase DoT aspect of Toxic Rain. The amount of pods you have at once (as per additional projectiles) can also scale DoT damage as they will overlap each other and STACK. 

The third one is the most interesting cause it does around 60 to 80% of our damage (with default gems). Explosions do area damage hits and, of cause, scale with your weapon damage. At the same time these hits can also apply poison and overlap each other, creating chain-pod POISONING explosions. The amount of pods on the ground is only limited by your attacks per second, pod duration and additional projectiles. 

There are FIVE ways how to scale pod damage directly and indirectly: weapon damage, attack speed, more projectiles, more pod duration (DoT), more poison duration (ailment). 

• With high weapon damage (high phys bow like Lioneys's Glare) and gems like Added Chaos, your pods will hit hard, but you will be slower as well. High weapon damage also means stronger poison hits. 
• With high APS and bows your pods will do around x2 less damage, but you will attack twice as fast, plant 2x more pods and overall will have much higher mobility. Will Blink Arrow much faster too.
• Using Dying Sun and bows like Death's Harp or quivers with extra arrow you will plant EXTRA pods. More pods = more potential damage. POTENTIAL because pods spread across the screen and not sit on top of each other. So, using gems like Greater Multiple Projectiles can be counter-productive in some cases. 
• Scaling Damage over Time aspect of pods with Increased Duration, Skill Effect Duration and adding Concentrated Effect, Efficacy or even Decay 
• Using Poison Support (in early game), Coralito's Signature and even Dendrobate can greatly scale and stack Poison on enemies, to a point where Poison goes AHEAD of your DoT damage even. 
• Vaal Blight and Spell Totem with Wither help with bosses, debuffing them for more chaos damage! 
• You can use Animated Guardian with classic setup to boost your Herald as well, if you wish! 

HERALD OF AGONY

Herald reserves a part of your mana and gives you increased poison damage as well as high chance to poison. 
When you poison an enemy with Herald active you summon an Agony Crawler scorpion and start gaining Virulence (caps at 40). Your Crawler is a MINION which does projectile and area attacks. So he scales with all kind of attack damage as well as generic minion damage and physical+chaos damage. Crawler also scales directly with Virulence stacks. You need to keep hitting enemies and poisoning them in order to maintain these stacks, and it's only possible with fast attacks, high chance to poison and decent mobility to chase monsters around. When you lose all stacks your crawler vanishes. Master Toxicist Pathfinder passive directly helps keeping Virulence stacks up! 

Path of building

Quill Rain: https://pastebin.com/KJGT2t3z

Lioneye's Glare: https://pastebin.com/AT6ADTY9