Herald of Agony will play an important role in this build. Herald of Agony is a herald skill gem. When activated it reserves mana and grants a buff that gives a chance to inflict poison on enemies, if the enemy is successfully poisoned the character gains Virulence and an Agony Crawler minion.

This build should be a pretty good choice for a league starter if you don't need to go super fast. Though you need to take a while to get all the desired items, if you take a look at the low budget setup you'll find that you don't need much to get it going.

Quick Jump

• Pros & Cons
• Playstyle
• Skill Tree 
• Gems Setup
• Gear Setup
• Leveling

Pros & Cons

Pros

• + Can do all map mods & content
• + You are immortal 83% of the time!
• + Works well on a budget

Cons

• - A bit weak to Degen damage
• - Not the fastest mapper
• - Getting all the corruptions can be hard/expensive

Playstyle

Lead the way for your Agony Crawler by going through packs and see how your personal Artillery Canon blasts everything around you. Use Tempest Shield and Convocation every now and then. The crawler is immortal and you are not far behind yourself.

Skill Tree 

Ascendancy

Painforged -> Versatile Combatant -> Violent Retaliation -> Blood in the Eyes

Bandits

Kill them all

Pantheons

The Pantheon List

• Major: Soul of Solaris provides many really nice defensive benefits for when you actually get hit
• Minor: Soul of Shakari. Poison Immunity.

Passive Tree

Gems Setup

Please note that this setup is not absolute. If you want to see the the setup for the Medium and Low budget builds, check the corresponding Path of Building builds found at section "POB"

Body: Herald of Agony - Pierce - Damage on Full Life - Minion Speed / Minion Damage + Vicious Projectiles + Vile Toxins (45-50% more dmg) / Maim / Empower 4 / Added Chaos

Getting 5 Off-colours on the Calamity can be hard, which is why I've included multiple alternatives for the 6th link.

Gloves: Cyclone - Life Gain on Hit - Fortify - Withering Touch - Faster Attacks - Poison

Note that I get 2 links from my gloves. Poison is a REQUIRED gem so if you don't have the gloves then you need to socket it. Lesser Poison is also a good option until you get an extra 20% chance to poison from gear or jewels.

Boots: Cast when Damage Taken (lvl 1) - Desecrate (lvl 7) - Spirit Offering (lvl 8) - Convocation (must be lvl 6 or above) / Increased Duration

For mapping, recommend Convocation instead of Increased Duration as Proximity Shield mobs will be very annoying otherwise. I Sometimes recolour my boots for Increased Duration when doing Über Elder.

Helmet: Tempest Shield - Curse on Hit - Temporal Chains - Culling Strike

Here you can experiment if you like. I love Temporal Chains but the only thing that's required is really the Tempest Shield. Abyssal Cry is also a valid contender here, especially if you pick up the instant cast warcry cluster.

Weapon: Herald of Purity - Withering Touch - Minion Damage - Maim - Faster Attacks - Melee Splash

Shield: Shield Charge + Faster Attacks + Blood Magic

If you don't use a Curse + Culling setup then you can use the helmet 4L for Shield Charge and throw in Fortify.

Ring: Hatred

The medium budget build will use Determination here instead to get the watcher's eye block. If you want to run Elemental Equilibrium then you want to link Hatred with Generosity, so you doesn't give the enemies +25% to cold resist. 

Gear

Overview

• Weapon: In most cases a rare Gemini Claw will be the best option. However, if you are on a budget or playing SSF then the Advancing Fortress is a great option.
• Shiled: Lioneye's Remorse is one of the best shields you can get, especially if you can manage to get the +1 to maximum chance to block attack damage corruption on it. Any unique shield that has life and around 30% block chance will make a good substitute to the Lioneye's Remorse.
• Helmets: Any helmet with the "Summoned Agony Crawler fires 2 additional Projectiles" will work. 
• Armours: The Calmning Calamiy
• Gloves: Rare Elder Gloves with Chance to block Attack Damage.
• Belts: Belt of the Deciever or a rare Leather/Stygian bel
• Boots: Any Rare one will do
• Rings: 1x Essence Worm
• Amulet: The Anvil. Try to get one with the 4-5% chance to block attack damage corruption. If you are SSF aim for life & resists here.
• Jewels: The Red Nightmare or a Watcher's Eye with +% Block when affected by Determination (reduced dmg from crits is a bonus here too) For the reamining rare jewels it doesn't matter much if they are regular jewels or Ghastly Abyssal jewels. Regular jewels can however be used to reach 100% chance to poison.

Flasks

This isn't a particulary fast build by itself, so the one flask I strongly recommend to get is the Alchemist's Quicksilver Flask of Adrenaline. It'll make a difference for you while mapping.

Rumi's Concoction is a great option for 2 scenarios. Either when running a -#% block chance map, or if you haven't been able to pick up all block nodes and/or gear.

The remaining flasks can be any combination of utility & life flasks. Just make sure that you have Bleed / Freeze / Curse immunities on your non-instant flasks and you'll do great.

Leveling

Link your character to GGG as early as possible, even if it can be wise to wait for lvl 31 and the Poison Support before you try commiting to it. Link Cyclone (or Molten Strike) with Poison + Lesser Poison + Life on Hit and get a Double Claw (Life & Mana on hit) with attack speed on level 36 and that will take you to maps. Herald of Agony should be linked with (in order of importance) Pierce + Damage on Full Life + Minion Speed/Minion Damage/LMP + Vicious Projectiles/LMP

Leveling Trees

• 40 points
• 67 points
• 88 points
• 99 points
• 114 points

Feel free to pick up the block nodes, more life nodes, or more minion nodes earlier. The Leveling tree's should serve as an outline to how you can do it, but depending on your gear and taste you can always go for what suits you better.

Up to level 55 when you can use the Coming Calamity, and if you don't have one yet, you can go for any other body armour. The mana cost for Herald of Agony with the links found in 4.1.2. isn't too high even on a 6L, so if you have a tabula go for it!

The 3 skills and links I would get ASAP when leveling are

• HoA - Pierce - Damage on Full Life - Minion Speed / Damage (for bosses) - Vicious Projectiles
• Cyclone - Poison - Lesser Poison - Life Gained on Hit
• Shield Charge - Faster Attacks - Blood Magic - Fortify

The remaining links you can pick up when you have the sockets & links for it.

I also strongly recommend to level 6 Herald of Agony gems in your off-sockets. Having a fairly good chance at getting at least one of them to lvl 21 + 20 quality will be very nice indeed.

PoB - High Budget: https://pastebin.com/tXmwLs8H (~1m dps)
PoB - High Budget - Insant Abyssal Cry: https://pastebin.com/3ByLrL68 (~900k dps)
PoB - Medium Budget: https://pastebin.com/PW9uw8Mq (~630k dps)
PoB - Low Budget: https://pastebin.com/1Pzc3Ym1 (~550k dps)
PoB - HC / Life Oriented https://pastebin.com/KbA5dNh8 (~450k dps)
PoB - Super High Budget https://pastebin.com/CGgpHmQg (~2.4m dps. With Molten Strike to keep 15 wither stacks up)