Level 100 CI Raise Spectre Necromancer^3.21

Notes

You are meant to use Forged Frostbearers with this build. Any other minion will feel bad, though you can run Syndicate Operatives with Triad Grips--I will include a gear-set for this.
I am using 120% More Damage on the Calculations to account for Anomalous Faster Projectiles with Syndicate Operatives... This is NOT meant to be enabled, if you update this POB with the FB spectres.
You will, however, most-likely need to account for the overlap when the new spectres are added. This can be done by multiplying the number of spectres by the overlap you're certain you will obtain. 
Keep in mind: with GMP, overlap is worse as they move further away from the target and will also depend on the target's hitbox.

=== NOTES AFTER TESTINGS ===
1. Predator feels far better due to the Ai wanting to move away from the target. You can soft-lock them on something and they will move less. It also ends-up being a DPS increase.
2. Greater Volley is better for everything. Don't use GMP/aGMP. aGMP CAN be better, but is less reliable and fully based on positioning.
3. I currently have the POB set to shotgun with one projectile less than cap; this is because after testing they do seem to shotgun fairly well, but you need the AOE from Plaguebringer and proper positioning
4. Awakened Spell Echo really isn't needed and won't increase your DPS by very much.
5. Soul Eater is an absolute life-saver for clear, run it. It should be one of your first purchases. These spectres are a bit slow for clear, so that jewel helps immensely.

Ghastly Eyes are CHEAP with ES and flat Cold, at the moment, since Ghazzy's build uses Life. I'd suggest buying these...

==== I've included both an HC and SC tree ==== 
HC obviously sacrifices some damage for SIGNIFICANT buffs in defenses (you'll go from 60k eHP to 110k eHP w/Near cap block / 100% suppression / 31k EV / 5k es)
SC obviously sacrifices defense for SIGNIFICANT DPS increases (you'll go from 5mil w/SO, using SO because FB isn't in POB yet, to ~10mil+ with the right gear)
You CAN use the SC tree, with the HC skill-setup, just remember to change your Ascendancy to self-offerings (pretty much the only change to the tree is Bone Offering vs. Spirit).

While many of these items can be pricey, they are not unobtainable and are meant to be worked on over the league; there is also much room for UPGRADES--Here is the short-list:

1. I used Two-Stone rings with resistances. You may be able to get these resistances elsewhere (jewels, gear, etc.) and swap to Bone Rings w/Attack and Cast speed + Damage.
2. You can absolutely go for 30% RMR on the shield + lv4 enlighten and fit in a level 20 precision for far more damage and potentially another aura, all together.
3. Mana can be an issue; feel free to craft mana/regen on rings. I took an enduring mana flask with Reduced Cost for QoL, but this is optional, if you can find other ways to reduce costs.
4. Minions do not use charges in this build; feel free to come up with a creative solution for this (charge sharing / gravebinds, min charges with NA, etc.)
5. Some gem alt. qualities are better than what is currently used.
6. There are some niche and hard-to-get mods that will heavily benefit this build, here's a few: +1 Maximum Spectres from Delve, Corruptions for +level, dropping Precision for Redeemer -X% cold res on helmet, etc.
7. Boots are used for +1 curse. You can drop them for rares with FAR more ES or EV and Elder w/+1-2 to Level of All Raise Spectre Gems
8. Ashes of the Stars fits in extremely well in this build. Assuming you can use Anomalous Faster Projectiles, you will be able to Convocate your FBs onto a boss and deal 3x+ damage (like how Nimis worked with CF).
9. Awakened Spell Echo is NOT included by default and is actually worse than some alt. qualities, if using Ashes of the Stars. Feel free to use either route.
10. You COULD take Iron Reflexes on Skin of the Lords, but your ES would go down; you would have far more Physical Max Hit and +1 level of spectres, though. I don't really recommend this.
11. Add a lab enchant
12. You COULD get +1 spectres on your chest, but it would probably drop the ES down by enough so that it's not warrented. If you can get this, with high es, then Eater/Exarch it with aura effect and you're GG.

There are also some very affordable items in the gear list: Rings, Amulet, Body, and Gloves are all fairly easy to obtain in SC. The attributes can be fixed with the tree, as well, if that's an issue.
I took a bit of a lazy approach and just added All Attributes in a few different places, but it's easy to just get these specifically on Rings/Amulet or other pieces of gear.

CRAFTING GUIDE (WIP):

Shield (most expensive piece):
Bound/Corroded/Dense/Pristine (Avg. tries ~70)
You do not need a perfect shield. As long as you get the RMR, minion mods are optional. I would recommend running Victario's until you get this rare shield with RMR.
This can also be substituted with min Frenzy/Power shield using Necro Aegis and results in very similar damage (or more, if using Ashes of the Stars, since you can maintain the same amount of auras).

Large Clusters
Crit reroll in Harvest is an easy way to always have Vicious Bite appear.
You can do this until you get the perfect set, but don't forget to set alerts for cheap jewels; many people put these up without understanding what they are.

Helmet
Buy a 100% base Hubris
Eater until RMR
Loathing until +2 Minion (~20 divs on average)
OR 
Buy a +2 to Level of All Minion Skill Gems Fractured helmet with either ES or EV/ES base (2~3 divs)
Spam Loathing for desired defensive modifiers (you're going for high ES)

Ghastly Eye Jewels
Buy or find i82 jewel base
Reforge Cold in Harvest Bench; it's very easy to hit desired modifiers (ES + Cold Flat, "Damage if you've used a minion skill" is a plus, but not needed).

+2 Minion Wand 
Fossil Craft with 4x Resonator using: Corroded + Jagged + Metallic + Shuddering. On average, it will take 12 attempts.
If you get a wand with an open prefix, great; if not, you may need to annul.
Craft "Trigger Socketted Spell when you Use a Skill".

Gloves (dex/int)
Spam Essences of Fear until you hit T1 Spell Suppression--that's really all we care about. Good resistances and ES are a plus.