Despite the title, this is not hardcore viable, but has been working for me in softcore. I've only made it to yellow maps but I'm confident in its ability to scale: https://pobb.in/MbmVTvmDTa1y

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The game is to combine Petrified Blood, The Golden Rule, The Tainted Pact and Strength of Blood for absurd defenses and recovery. Petrified Blood gives us overleech, Tainted Pact gives us chaos damage over time as life recovery instead of damage, The Golden Rule gives us poison reflect onto ourselves for the Tainted Pact recovery. And, since we have something on the order of 30,000 life per second from Tainted Pact we don't need actual life leech, so change it to less damage taken with Strength of Blood, and add in Atziri's Acuity for Vaal Pact when fighting so we can take even more less damage. It's not like we need life regen anyway. Apep's makes the self poison last for 4 seconds allowing us to get more stacks and also have more safety when moving between packs to not get killed by rage or blood rage degen, and the extra +3 max elemental resists is a nice extra defensive bonus. I built out of a berserker because blade flurry without mountains of attack speed feels terrible to me. Finally, while not in the PoB, I recommend putting enduring cry in your links somewhere to have a way to heal when not in combat, such as during boss mechanic phases.

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Three things to be careful of with this build:

1. Don't run low level content. You will not create a large enough leech instance to keep leech running for 5 seconds, meaning you'll stop leaching and the 4 second duration poison you reflected onto yourself will kill you.
2. Don't run temp chains maps. They will increase the duration of poisons on yourself beyond the 5 second leech duration and, when the leech duration ends, the poison will kill you.
3. Don't put a life flask on your flask bar. If you do, you will accidentally hit it, it will heal you to full health, your leech will end, and the poison will kill you.

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Monsters that can't be leeched from are a concern, but as long as there are other monsters nearby you can leech from you should be fine.