Level 99 Herald of Agony Juggernaut^3.25

Notes

In order to level this build as a Herald of Agony Herald of Agony build you need to make your way to level 16 to be able to use the gem, and you???ll need a Quill Rain Quill Rain for the most optimized HoA leveling. If you???re not planning on getting a Quill Rain at level 16, you want to delay the transition until level 28 when you can get Cyclone.

Getting to Brutus & Merveil
For starters, create a Marauder in whichever league you want to start.

You will want to start out by buying two Axes from the vendor. On top of that, pick up a Molten Strike Molten Strike or a Perforate Perforate as a quest reward. After you???ve run the Mud Flats, you???ll proceed to kill Hailrake in the Tidal Island with Perforate or Molten Strike.

From there on, you???ll be able to pick up your first Quicksilver Flask Quicksilver Flask and an Ancestral Call Support Ancestral Call Support from your quest rewards and perhaps a Chance to Bleed Support Chance to Bleed Support and an Momentum Support Momentum Support from the vendor. Your main Molten Strike Molten Strike link should look something like this:

Molten Strike or Perforate
 Ancestral Call Support (only if you???re using Molten Strike)
Chance to Bleed Support 
After killing Brutus, you will be adding an Added Fire Damage Support to your Molten Strike/Perforate link, replacing the Chance to Bleed Support.

Transition to Herald of Agony at 16-18 with Quill Rain
For starters, it???s important to know that Marauder doesn???t get a lot of the Skill Gems required for this leveling process. Therefore, in a Solo-Self Found environment, you???ll have to progress to Act 3 Library in order to buy them from a vendor. If you???re playing Trade League you can obviously ask someone in global, a friend, or worst case just go buy them on the official trade site.

The reason why the transitioning becomes so much easier when you have a Quill Rain is the base Attack Speed the bow offers. Because of its insanely high attacks per second, keeping up Virulence stacks will become really easy, even at low levels and low increments on Attack Speed. You???re going to use Rain of Arrows to maintain stacks, as it can hit a single enemy multiple times and thus generate multiple stacks per attack.

Rain of Arrows 
Chance to Poison Support 
Faster Attacks Support
Herald of Agony 
Vicious Projectiles Support (requires level 18)
Damage on Full Life Support  (requires level 18)
Pierce Support Pierce Support / Faster Attacks Support(use Faster Attacks for bosses)
In the case of the HoA link, it will obviously only be possible to add the 4th gem when you obtain a 4-link. Do not worry too much if this is not yet the case for your character.

Transition to Herald of Agony at 28 without Quill Rain Quill Rain
If you can???t get a Quill Rain early on, and you really want to swap earlier, you could use Storm Brand and rush the Runebinder Keystone for 2 Storm Brands per Enemy. Your link would be:

Storm Brand Storm Brand
Faster Casting Support 
#Chance to Poison Support 
Otherwise, you can start using Cyclone at level 28. Cyclone inherently feels good to use while gathering stacks for your Crawler and therefore is chosen. Your Cyclone links for now should be:

Cyclone Cyclone
Chance to Poison Support
Fortify Support 
Faster Attacks Support or Life Gain on Hit Support
Whether you use Faster Attacks or Life Gain on Hit depends on your overall amount of Virulence. If you feel like the stacks / damage of your Crawler is doing fine, then Life Gain on Hit obviously provides a decent chunk of Defenses, otherwise Faster Attacks gets you more Virulence uptime.

Your Herald of Agony links are the same as they were in the Quill Rain setup. Should you be playing with a Tabula Rasa you can add Maim Support and Minion Damage Support. Otherwise, as you???re stuck on a 4-Link you can add a Hatred Hatred linked to Generosity Support in Act 3 / After Library Quest.

Crafting a +1 to Level of all Minion Skill Gems Helmet
Very few people actually realize this vendor recipe exists but it is a GREAT help for leveling Summoners! Now, to acquire this helmet you will need the following items:

Any 4-Link (Normal) Helmet
2 or more quality gems with a combined total of 40% quality & the Minion tag
you???re gonna sell the helmet and the 40% quality of minion tagged gems together and it will return you the helmet with +1 to Level of all Minion Skill Gems

Level-ups are really strong for your Crawler though, so don???t skip this step!

The Holy Relic & Other Buffs
Whenever you get the possibility to get a Summon Holy Relic Summon Holy Relic setup rolling, especially with the Feeding Frenzy Support Feeding Frenzy Support, that???s a huge bonus to your Herald of Agony Herald of Agony. Additionally, setting up a Cast when Damage Taken Support Cast when Damage Taken Support with all the buffs linked will provide a lot of help as well.

Summon Holy Relic 
Feeding Frenzy Support
Cast when Damage Taken Support Cast when Damage Taken Support (Level 2)
Spirit Offering  (Level 8)
Desecrate(Level 8)
Sniper's Mark (Level 6)

Leveling Trees
We created a leveling Passive Skill Tree you can use to get an idea of how your build should be looking at the transition point. From here on out, you???re really just gradually completing your Endgame Passive Skill Tree. Here is what you should go for : https://poeplanner.com/b/8_K

Useful Leveling Unique Items
As you begin a new character, there are a couple of items that can make your leveling process a lot smoother. Tabula Rasa allows you to have a 6-Linked skill as early as you are able to use specific support gems. Wanderlust gives a decent amount of movement speed, which will make your leveling that much more efficient and a Goldrim provides a lot of Elemental Resistances which help a great deal during the leveling.

If you are a new player (or if this is your first character for the league), note that obtaining these items will be very difficult, if not impossible. They are rare drops, which you can otherwise only acquire if you have saved up currency, so do not focus on them too much, and instead simply look for items that match the affix priorities listed in the Gearing section.