On early map setup, feel free to drop 1x lori's for a rare ring if you can't manage stat requirements at all. But should be doable. Try to get armor bases early, if not doable get items with high int/dex rolls.
AG Priority Early:
1. Leer Cast
2. Dying Breath
3. Legacy of Fury
4. Chaos res cap on chest/gloves
Spectres:
Start with 2x Frenzy monkeys.
When your merc has a frenzy chest -> swap to perfect warlord (endurance charge generation) + Forest Warrior (Onslaught / cull). If you feel like onslaught uptime is good enough from the spectre alone, feel free to swap the silver flask for something else (granite maybe?).
Your Spectres & AG are probably gonna be a bit squishy at the start, but should be OK when you get the helmet for DR on them.
Snipers mark or Flammability:
If Soulthirst merc use Flammability.
If Enmity Merc use Sniper's mark.
Hallowed Monarch Info:
The helm does NOT give your Merc Headhunter. Mercs are Allies, not Minions.
For the helm to do anything (besides damage reduction / light radius) your AG needs to have gravebind equipped, which then steals the kills from the merc (if in range) and provides some HH buffs to your AG and Spectres to increase their tankyness.
How does Ceinture of Benevolence + Soulthirst on Merc work?
Ceinture applies our flask to our linked targets as well (our merc + our AG + our spectres). We still get the all the normal effects of the flasks, they are not removed from us.
Soulthirst gives the Merc the ability to get Soul Eater stacks whenever he kills an enemy during any flask effect. Normally Soulthirst resets the soul eater stacks when you use a flask, however since the Linkbot is using the flasks and not the merc directly, the stacks are never reset.
Soul Eater still automatically decays by 5 stacks / second after 2 seconds of not gaining any stacks (aka killing anything), which means for bosses it will be at 0. However during maps after killing 45 monsters and if you keep killing while clearing the map your merc will enjoy 225% increased attack speed during the whole map.
This gives us up to triple damage during mapping / high density content because attack speed normally is very hard to get on mercs.
When to swap away from pet blood?
When you have 2 Vermillion rings with T1 life + T1 Light radius. This is most likely somewhere between midgame and endgame setup.
Enmity vs Soulthirst Merc:
When you do the swap to an enmity setup will highly depend on the content you are doing:
If you are doing mostly single target stuff (e.g. T17 bossrush) then swap ASAP and use another belt yourself (stygian with good life / life%). Can then go for rare weapon/shield and run untouched soul for more res if the merc gear isn't that good yet.
If ur farming e.g. breach/legion with a ton of monsters then I'd stay on the soulthirst setup the whole time until you have your Mageblood.
Soul eater got nerfed to 2 sec duration before falling off, but if you are doing dense content soul eater should be sustainable.
Keep in mind for emnity to be good you need a good roll on it which will be expensive.
How to play?
1. Link your Merc, AG and Spectres at the start of the map
2. On bosses / tanky rares selfcast your curse (if you feel like you need it ofc)
3. On bosses / tanky rares throw down stormblast mines (if you feel like you need it ofc). You can pre-stack theses as well during phases.
From the Midgame onwards your mines last a long time (~9 secs) and are immune to damage, which should allow you to easily maintain all 18 mines on bosses (4 throws with minefield). !! DO NOT DETONATE THEM !!
4. Shield charge + frostblink through the map and watch ur guy onetap the whole screen.
What skills do I want on my Kineticist?
The main damaging skill on the Kineticist is Kinetic Blast of Clustering. For supports it's Return Proj >>> GMP >>> 1 Clear link (Fork/Pierce/Chain) >>> Ele Dmg >>> Crit dmg >>> 2nd clear link >>> added dmg (all useless we have thousands of flat).
Your Merc MUST NOT have Kinetic Bolt or Barrage. Both have alternating prio with clustering and makes the Merc alternate skills which is instantly half dps.
The best secondary skill is Greater Kinetic Blast (has a cooldown of ~10 secs so barely matters).
Best support skills are Haste > Inspiring Cry.
Many people say Frostblink bugs the guy, but I played hundreds of hours with a frostblink merc and didn't notice anything.
Ele Weakness from the Merc will never be applied, as both you and your merc have a curse limit of 1.
How do I level?
IDK what's optimal, my personal plan will probably be sunder until I find a merc that's playable -> continue sunder but spec towards map start tree. Sunder has the tree that shares the most points with my planned early maps tree, so the respec is manageable just with gold + campaing respec points.
Havoc has a great Scion Sunder Leveling Guide on Maxroll that I'll be following as well roughly since I suck at leveling. Link:
https://maxroll.gg/poe/build-guides/scion-leveling-build-guide
You want blood magic specced when you start flame linking your merc otherwise mana will be annoying.
After getting blood magic either run eternal blessing + purity of elements or haste, depending on how confident you are.
You might want to keep reserving precision and optionally vitality on life immediately as well.
Do not gamble with your gold, you will need your gold to respec to the map start tree.
And finally: Don't expect this build to giga speedrun the campaign/map start. You will have to do some testing with mercs / maybe some fishing for mercs in act 3.
Map Progression
During Map Progression it might happen that you find a good other DPS merc besides Kineticist - feel free to just experiment around since you have 3 slots.
I'd always keep at least 1 good merc in reserve incase a new test merc does not work out.
Good Mercs are the Molten strike guy, bow guys, blade trap guy, 1 more melee purple balls guy. These have all variing levels of clear and single target.
When you hit T16 maps keep an eye out for a decent smoulderstrike merc and keep him in your back pocket for single target bosses. Could be better to use that guy then for voidstone bosses / single target stuff early on. (just swap your whole gearset over and get a weapon)
GGG announced that there will be Merc points on the atlas tree as well. If there is merc spawn chance i'd HIGHLY recommend rushing these, as buying contracts early most likely is not an option / a waste of early currency.
Help my merc is dying!?
Get Leech on the merc
Get the Perfect Warlord spectre for endurances for the merc.
Get gear with actual life rolls
Get Chaos Res capped.
Maybe use evasion bases / get some suppress.
And Finally get more damage -> he can't die in a map if he onetaps everything.
Gameplay Showcases from Merc League:
https://www.youtube.com/watch?v=al2KmjudHDA
https://www.youtube.com/watch?v=s7WdKz1sEyE
Follow me on Youtube for Build Updates / Showcases or even the occasional stream during the league start :)
https://www.youtube.com/@nerotox813?sub_confirmation=1