TL;DW The Guardian turtle spectre can have 100% uptime on the damage immunity buff, making you unkillable.

PoB - https://pobb.in/lobo5bjcDpjK

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On the main subreddit check out the associated meme clip using Stereo Saiyan 3D as the soundtrack, I personally enjoyed making it more than this video xd

Longer Explanation (video is still far more detailed)

Guardian turtle can cast a buff on the player, normally granting 2 seconds of "You Cannot be Damaged". By linking More Duration + Efficacy + (Greater) Spell Echo to Raise Spectre and juicing up Malevolence aura, THEN going self-curse Temp Chains to make time pass 4x more slowly, you can achieve 100% uptime and run through maps while being entirely immortal. This is mostly consistent, but turtle AI is not the best and you can still die especially at the start of maps/Mirages when your turtle hasn't cast yet. If you're a bad pet owner, your turtles may not want to keep you alive :p

I made a trauma stacking Static Strike of Gathering Lightning Guardian, but you can make different builds abusing this mechanic. Reaching lvl 100 and playing really hard content is perfectly doable--who knew, being immune to damage makes PoE easy!