Diablo 2: The Brother (And Sister)hood of EoFF

[Tavrobel]

I have four spare Io runes. Runes aren't too much of an issue.

Few Poison enemies have >120% Immunity. Lower Resist, when against an Immune enemy works at 1/5th ability. You shouldn't worry too much, since Facets are applied afterwards. If Immunity is broken, Facets do full damage, which is more important than LRes working at full capacity, because Facets do not affect Immune enemies until Resistance has been broken.

As for Mercenaries, Holy Freeze, I assumed was always level 10, or it might be based on leveling.

After doing some research, these are Poison Immune monsters, by Act:
Act I:
Skeletons (< 105): Returned, Bone Warrior
SArcher (< 110): All
Hawks (< 110): Foul Crow, Blood Hawk, Black Raptor
Spiders (< 105): Poison Spinners

Act II:
Maggots (< 125): All
Baby Maggots (< 100): All
Vultures (< 110): Carrion Birds
Mummies (< 110): All
Spires: Cannot be broken
Fire Towers: Cannot be broken

Act III:
Mosquitoes (< 110): All
Frogs (< 110): Slime Prince
Spirits: burning Souls (unknown number)
Bone Fetish (< 125): All
Tentacle Beasts (< 110): All

Act IV:
Great Demons (< 100): Nightmare, Venom Lords
Corpse Easters (< 110): All

Act V:
Catapults: Cannot be broken
Reanimated Horde (< 100): Nightmare and Hell, Unholy Corpse, Defiled Warrior
Succubi (< 120): Vile Temptress, Blood Temptress
Defilers (< 120): All
Pain Worms (< 100): Menace Worms

With a level 20 Lower Resist, you cannot break the immunities of those with 110+ Poison resistance, which is only the top two of the "All" monsters categories. Since LRes does 67/5, that is roughly 13%. Facets cannot break Immunity, unless they [monsters and Immunity] have already been broken.

As a result, either your Golem, Mercenary, Party ally, or regular Corpse Explosion (should you opt for it), can deal damage otherwise. This is a rather sizable number of enemies, and unlike most others, Poison Immunes are found in popular MF areas.