Need some advice on Chaos Damage

First time on forums, so please spare me some mercy. Thank you.

So my question is on Chaos Damage, and making a Poison Arrow build.

What can I do to lower a monster's/boss's chaos resistance?

So far I have done some calculations that makes the damage quite significant with the Stage 2 damage-over-time effect on Poison Arrow. However, there are a lot of monsters and bosses out there that are resistant to chaos damage.

Any help is very much appreciated.

Nothing, there aren't any skills that can lower chaos res. On the plus side, there are no 'chaos resistant' mods for magic and rare monsters and also no chaos res auras or other effects.

You can use Vulnerability to squeeze more damage out of it, high chaos res isn't exactly common and Poison Arrow is quite strong so it doesn't really need much help.

Alright, but what about story bosses? They have resistance to chaos damage. Is it 100% immunity, or a certain percentage of resistance? I can never tell.

It seems in PoE there are no immunities to elements and chaos.