This is a build that I have been theorycrafting and playing over the last couple of weeks.

Mapping, Conquerors, Sirus and Shaper showcase

POB: https://pastebin.com/9kg1Qiwd

##Build Mechanics ##Self-Cursing The build uses [Rotblood Promise] to self-curse with Temp Chains and make nearly all duration effects last 4 times longer. I've played Self-Curse with Headhunter + Inspired Learning using [Shackles of the Wretched] before the Hexproof changes and when Rotblood was introduced I felt like it wouldn't be worth losing 43% curse effect from hextouch/enhance + the reduced effect of curses from the ring. Now I feel like even 100% reduced effect of curses would be worth it because it adds so much consistency, especially defensively. Not only are all enemies on the screen slowed with 235% increased effect, flask and and most skill durations get extended unconditionally.

Additionally we curse ourselves with Vulnerability via Coward's Legacy to gain Access to Pain Attunement and gain 60% increased effect of curses on us as a side effect. As the Vulnerability ends up with 136% increased effect, we have to find a way to deal with that. Unaffected by Vulnerability Determination Watcher's Eye seems to be the only way to do that without messing with Temp Chains.

Due to our investment into curse effect we end up with strong Despair and Assassin's Mark as a side effect.

##Immortal Call This is the key our tankiness. By itself it gives us a respectable 30% less Physical/Elemental damage taken plus another 60% less Physical from our 4 Endurance Charges. [Veteran's Awareness] is completely nuts on this build as it gives another 10% max Res (~50% less Elemental Damage taken) and 20% Physical Damage Reduction. The downside of 20% more Damage taken is only really effective during the cooldown (2.5s), otherwise it is heavily outweighed by the positive effects.

Immortal Call lasts for 13.4 seconds, which means it has an uptime of ~84%. Combined with other conditional but high uptime buffs like Vaal Grace, Replica Rumi's Concoction and Frost Shield we can reach pretty high numbers of effective maximum damage taken. Literally 1-2 million ehp against non-unique monster hits (if you consider 75% less action speed to be a 75% less Damage dealt modifier). Against Dots we only reach up to 50-70k, although we are immune to poison and bleed dmg (from Apep's Supremacy) and have high ES recovery (~33% ES/s from Vaal Discipline, 10% from Leech and 30 ES/hit from Watchers Eye).

During IC's cooldown however the build can turn into a 4.5k ES build with 20% more damage taken and WILL randomly die, especially since Vaal RF and Frostshield occasionally drain 80% HP... There are still other defensive layers, also most mobs never get to hit us and we can play around IC downtime when fighting bosses. Altogether one of the tankiest builds I've played, most of the time being able to tank Sirus Storms and Die Beams.

##Soul Eater We gain a 80 second Soul Eater buff from [Zerphi's Heart]. Sadly the duration does not get refreshed when using a Vaal Skill before it ends. For this reason it's best to not use a certain Vaal Skill (Vaal Haste) when Soul Eater is about to end, as it will then be ready to instantly regain Soul Eater. We can reliably generate about 40-150 Souls when bossing from Vaal Breach alone.

##Vaal Auras The reason for the build's name. I was also considering Vaal/Krangled Aurastacker but I felt Forbidden had a nicer ring to it.

The Vaal Skills we use are Clarity, Discipline, Righteous Fire, either Haste or Grace and Vaal Breach. They all have a 100% uptime during mapping and 60-100% when bossing. However Clarity and Vaal Breach are the only really mandatory skills and they can be up permanently.

So how do we sustain the Vaal Skills, considering they all have a Soul Gain Prevention of between 8 and 40 seconds? Since Soul Gain Prevention is affected by Skill Effect Duration but not Temp Chains, Self-Cursing is the only way to make Vaal Skills last longer than their Soul Gain Prevention (except for maybe some Triumvirate Authority + Soul Catcher with flask effect shenanigans? pretty sure that would require legacy items tho).

As to how we actually get our souls leads us to the next section:

##Flasks Soul Ripper. Two of them with nearly max charges used. 300 Souls + 20% reduced souls used from bloodstained fossil = more than enough to cast our entire Vaal Skill rotation. Also during mapping using one flask gives enough souls to cast everything except Vaal Breach, which we don't need in that scenario anyway. During mapping it will fill up, so you can use it before a boss if we lose Soul Eater or don't have a lot of stacks yet. Ok now that we can basically convert flask charges to souls, how do we gain our charges? This is the painful part of the build. Since Soul Ripper flasks lose all charges when entering an area, a downtime of Vaal Skills and Soul Eater at the start of a map/boss fight is unavoidable. However during mapping I usually fill up my flasks fairly quickly, about 15-30 seconds into a map depending on density.

When fighting bosses without mobs we can use a [Overflowing Chalice] and then unquip all flasks except the Soul Rippers and gain ~12 Charges per empty Flask Slot from [The Traitor] Keystone. The flasks take about 20 seconds to fill up that way. Can be annoying but it's only really necessary for Maven/Sirus/Elder or after dying. It is also possible to gain charges during Grace Period(which lasts for four minutes btw) you just can't use Overflowing Challice, which means it takes around 50 seconds to fill the flasks.

During bossing, Vaal Breaches will almost always spawn enough monsters to fill up Soul Rippers (depending on arena size). We can drop some Flasks to gain more charges for bosses with small arenas (so far only Olroth and sometimes Shaper). The timing of Vaal Breach(40s) and Soul Eater(80s) works out quite nicely and requires very little management keep up permanently.

This Vaal Breach/Soulripper combo is IMO the most broken/unintended mechanic this build uses, especially since you can get permanent Breaches during Bossfights with way less Investment, just a Flask Slot and a timeless jewel Keystone basically. It still feels kind of balanced since it comes with a waiting time of at least 20 seconds.

Replica Rumi's Concotion is a really strong Flask for this build as we can make it last for nearly 20 seconds with Enkindling Orb and are unaffected by the Petrified effect.

Additionally a Diamond Flask with crafted Crit chance and a Quicksilver with Ignite removal, both with increased Effect/reduced Duration.

##Cost Not really sure but definitely not a budget/league starter build. Most of the items are not extremely expensive (all <10 ex), however the build needs very specific items, a lot of them self crafted. The build is starved on Skillpoints, Resists, Strength and Dex, sockets and even keys to use all the skills (trigger weapon helps). Currently I've spent around 60ex on the build but it could be done a bit cheaper.

Building the character reminded me very much of Aura Stackers, since it takes a lot of investment, high level and very specific gear to pull off. Because of the inconsistency in tankiness and an unavoidable weak phase at the beginning of a new area it is certainly not as strong as a fully decked out Aura Stacker, but still a very fun build to play.

About 10-20M Sirus dps are possible, but it takes some time to ramp up (Soul Eater,Wither,Poison stacks), so the damage is ok but not insane. Without buffs at the start of a map the build feels very weak, but Profane Bloom heavily carries our clearing.

##Future Ideas Going all in on poison would be very strong, considering the juiced up Temp Chains/Enfeeble. I haven't yet managed to make a POB with more dmg than this hybrid hit/poison version however. The last time I played a poison build was back in the double dipping days, so maybe someone more knowledgeable can find something there. Cospri's Will might be a good option for a life based build.

As we already have Determination + 60% increased Armour from small cluster jewels, we could reach 20M+ from the veiled +Armour during Soul Gain Prevention mods on Chest and Shield.

The setup should theoretically work with any Skill, I really want to try out Winter Orb and maybe Eye of Winter. Either as cold Occultist or poison with Volkuur's Guidance.

Initially i wanted this post to be a quick showcase of the build and describe the mechanics a bit but it turned out longer than expected. If there is interest I could still write up a proper build guide and go more into detail on the gear, crafting, playstyle, etc.

##TL;DR Dual Self-Curse, Self-Poison, permanent Vaal Auras + Soul Eater + Vaal Breach, Self-Cast Forbidden Rite Occultist with 10M+ Sirus DPS and 1M eHP^(most of the time)