This is life based. Bane for trashkilling and debuffing bosses. Essence Drain to help with the tankier things. Wither totems as well.
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Auras:
Grace. Determination. Malevolence. All very good.
Until high level you can't take all three auras, just play around with different ones to find out what is best. I suggest skipping Grace early, Determination + CWDT Molten Shell is likely better than any combination with Grace.
Consider Purity auras as problem solvers. Purity of Elements, or even a single element version.
If your gear has little/no mana, mana will be BRUTAL. You'll likely need to get some. We are in Delve, so 'curse/mana items' nodes are all around.
Might also want to consider other options like Tempest Shield and Defiance Banner. This needs to be tested.
I will default to Determination, Tempest Shield, Defiance Banner, Malevolence early, turning them on in that order.
Items with mana reservation efficiency are hard to get but VERY good. Alpha's Howl is a tier 3 unique, Redeemer necks are another option.
Discipline isn't good enough. Skip it. Honestly even on an ES version use Determination.
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Incoming hit mitigation:
Moderate investment into both armor and evasion here.
Curse Mastery: I've gone with Hinder, however the blind option is really solid too. Won't fault either choice. For a graph that may help with the decision,
https://www.desmos.com/calculator/wd8hufux8g
You can also go heavy block if you want (quite a different tree) with the absurdly broken shield Remnant of Empires (30% spellblock) and Tempest Shield. Take Mystic Bulwark and a little more spellblock and you are capped.
Attack block will actually be the hard part! Or you can use a different shield and take more shield spell block nodes. Or try staff block (definitely do this if you hit the miracle staff detailed below under Extreme Upgrade Path)
Another option: As we are near Pain Attunement, we could go Petrified Blood low life. This requires all the recoup nodes north of Witch which are strong.
VERY important: Use level 1 CWDT and level 9 Molten Shell. I do not recommend high CWDT, although if you want to use one, you be you.
OPTIONAL: Vaal Molten Shell (create via Vaal Orb on Molten Shell)
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Ascendancy:
I consider Malediction, Void Beacon and Withering Presence 'mandatory'. Profane Bloom is the recommended fourth point but I won't fault other choices.
Note that Profane Bloom is needed for Punishment to be solid.
If no Profane Bloom, go Enfeeble as 3rd curse. Or use a damage support instead.
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Curses:
Despair is best offensively. Temp Chains is best defensively. Enfeeble is second best defensively
Punishment is probably the number 3 choice. Modest extra damage. Explosions chaining is amazing but inconsistent - works better in trade where you have better crafting methods (veiled mods) to scale chaos damage % more.
Even though you can get veiled mods in Endless Delve (Legion or Veiled Chaos Orbs) it seems you can't unveil them.
If you want to spec more into Punishment/Profane Bloom shenanigans, take the chaos damage nodes near Shadow start and the Heart of Darkness side of the chaos damage cluster. This will have to come at a price.
If you get a Chaos large cluster this is also an option. These might be quite rare.
Can definitely use 2 curses and a third damage support like Efficacy. If you do, drop the Whispers of Doom cluster.
On a five link, it's definitely 2 curses 2 damage supports.
Four link, 2 curses 1 damage support (note: this is different to accepted best practice prior to 3.15)
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Crafting notes:
Wands: 1 in 12 to hit +1/+1 by using an ilvl 55-82 NON-INFLUENCED wand with Shuddering, Corroded and Metallic fossils.
https://youtu.be/tRQhFHQeQyc
Reason: i82 or lower 'bans' the Malicious prefix. Shuddering, Corroded and Metallic collectively 'ban' all other prefixes except three. Spell damage%, +1 all spell skills, +1 chaos spell skills.
Also buffs the Despair curse.
+1 all gems also is solid defensively (Grace, Determination)
Shield: Pure Int shields can roll +1 Chaos skills. 1 in 16 with just Aberrant fossils. 1 in 20 with Pristine + Aberrant, but the hits will be better. NOTE: this CANNOT be rolled on any shield with non-zero armor or non-zero evasion.
Alternately, go defense.
I think I prefer a defensive shield personally (like a rolled Pinnacle Tower Shield, with its good balance of block% and armor, Vaal Buckler for the best block% in the game, or any of the top Dex/Str shields, Spiny, Cardinal or Elegant)
Archon Kite Shield might also solve problems with its 12% all resists.
Rings: Iolite or Amethyst bases prob best (don't use the Cerulean I have in the POB, they are intentionally mediocre)
Like the glass cannon playstyle and confident in your ability to mechanically dodge and/or preemptively use Molten Shell or Steelskin? In that case, use two wands.
EXTREME UPGRADE PATH:
i82 Staves are 1 in 40 to hit +3/+2 to chaos/all spells using Aetheric + Corroded + Metallic + Shuddering. You probably won't hit this, but it is the best use of the limited 4 socket resonators you will find delving. If you hit this while recording
your gameplay please squawk like a chicken and email the video to me.
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Tabula vs crafted 5L vs other options
6 links will be rare. Don't count on one.
If you go for a 5L, 6 socket first before trying to 5 link. 1 in 14 times you will accidentally hit a 6L first.
Tabula and 5L Carcass Jack are among the best options but they are rare.
Tabula can be 'farmed' somewhat in very low tier content - fractured walls drop a lot of uniques. Tabula is common enough at very low level as there's just not all that many uniques that can drop at those monster levels. However this process still
is not overly fast, and I'll leave it up to you.
Vaals are believed around 1/45 to hit a 5 or 6 link. 1/144 to hit 6S6L, 1/144 6S5L forward, almost no chance at 6S5L backward, 1/120 5S5L.
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Wither Totems
These more than double your damage when needed. They are only worth using if a miniboss takes 5+ seconds.
If you love Decoy Totem, you can use one but don't link it to multiple totems. You can then have 2 Wither Totems and 1 Decoy, or 3 and 0. I'm starting without Decoy.