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What does night herald’s 20% weapon damage to drain essence actually do? Is it adding 20% of weapon dmg to the existing spell dmg (100% spell dmg + 20% weapon), or is it taking 20% of spell dmg and is transforming it into 20% weapon dmg (80% spell dmg + 20% weapon dmg)?
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In case I dual wield 2 night heralds, will the weapon dmg be 40% (20%+20%) or will it be 24% (20% + (20%/5))? How is it calculated?
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With night herald’s weapon dmg, would I be able to leech energy with the nodes from viper and revenant or not?
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Since I’ve fallen in love with night herald dagger and spectral war shield, I’ve decided to use them for the end game. Based on your experience, do you recommend going dual wield with two daggers or going with the dagger and the shield? I know there are great legendaries, but I just want these two in the main and off-hand slots and yet I cannot decide between the two options.
I’ll let @Evil_Baka answer mechanics questions. Just wanted to ask
Cannot you just use their illusions on better items? Btw this is my SSF Cold DE at the moment (Veteran) 
I love the build. Unfortunately I’m not planning to use a shield in the endgame and won’t be able to use Spectral War Shield’s illusion:
Illusion
Yes.
Yes.
Yes but the effect will be scaled down to 20% or 40$ of the energy leech on Revenant/Viper. Sounds low but if you apply it to for example 5 enemies in a crowd, it might make up for it a little.
Keep in mind that Drain Essence scales on casting speed and that for a caster, having some cooldown reduction is also valuable.
If you opt to go dual daggers, you can consider taking Star Pact to circumvent the loss of CDR that an off-hand would offer.
Personally, I don’t see much merit in the Spectral War Shield for a Cold DE character - the Retaliation stats aren’t doing much for you and for everything else, an off-hand would be better in every way.
It’s old but I once tried putting a rough sketch for DW Night Herald DE together and it came out like this if you want some ideas: https://www.grimtools.com/calc/L2JYrBkN. Since it was a pure theorycraft and not something I planned on playing, I went nuts with greens 
It’s both the visual and the effect that the items have that attracted my attention. Love the wintry character look of the character. 
@Evil_Baka Thank you for answering my questions about the mechanics.
Is cold pact’s damage and cast speed worthy replacement for nightblade’s night’s chill resist reduction. I’m not sure it is, especially since both arcanist and necromancer lack cold resist reduction. Not to mention that main and off-hand slots are reserved with the daggers, so I can’t use resist reduction from other weapons and off-hands.
I feel you. I’m on a Green MI crusade atm. 
here is a version I theory crafted https://www.grimtools.com/calc/eZP8Y0PZ does not focus on wpn dmg to DE at all
No hence “theory crafted” 
Well there’s of course this build. But personally I’m not going to use Chain Lightning as I prefer having Whirlpool from the visual point of view. Thankfully Resistance Calculator shows losing % Reduced Target’s Resistance is not a huge loss. And also Energy Regen devotions Scythe and Harp because they can be a part of a good map. But other than that will probably be very similar to the build below.
You’re using Night Herald yet you recommended Ugdenbog Chillstrife to me? Please explain! I have Message Proof for this.
Also @Ulvar1 since you already using Hagarrad wouldn’t it be possible to use full Chillwhisper that gives bonuses to this rune?
Because this is not a reaper?
and also, tbh, I think I meant for leveling purpose chillstrife would be better than night herald bc you wont have that much wpn dmg to apply early on
True, wasn’t thinking too clearly on this suggestion, late night 
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