"monsters penetrate % res" help

I have "Monster damage penetrates 12% elemental resistances" as a delve modifier. I don't think I've seen a modifier written like this. I feel like I've definitely seen the debuff "lightning penetration" on me in maps - I remember seeing my total uncapped go down but max res remain unchanged on character sheet. Looking at the wiki it makes sense that the max wouldn't change, but I don't think uncapped should either going off that. It's my understanding that in this case, I would basically have effectively 88% of my max ele res in this zone. I.e. I would be taking damage with 80% ele res as if I had 70%. If it's gonna feel like 70 res, I probably path around it in hc. 50% damage increase against ele hits??

Help.

I don't think it works off a percentage of your total resistance, I think it just goes through the flat value of 12. So 75 res is treated as 63 (not 66).

It could be a dangerous mod in HC, particularly if combined with other ele mods.

If your character defense is largely based of max res it might be particulatly bad. Its worse the higher max res you have. 90 to 78, 22/10=2.2x. 75 to 63, 37/25=1.48x. If you have other layers like evasion, it mightn't be so bad, but will still lower your max hit taken.

https://www.poewiki.net/wiki/Resistance_penetration#/media/File:Resistance_penetration_efficacy.png

- Double post, can be removed

Thank you. I believe you're right in the examples. I pathed around the big cluster of them but found another one I went through. It wasn't great.

Yeah sometimes can be hard to find a safe path. Having over capped res might help if you don't already. Not with the penetration, but incase you combo'd with any curses or exposure that might make it worse. Looks like your going pretty well with your build. Those mods mightn't be so bad for you with the recent endurance charge changes.