If it says 100 damage over 5 seconds. Does it mean 100 damage per seconds, so a total of 500 damage is inflicted? Or is it 100 damage dealt spread out over 5 seconds?
The damage number is the total amount dealt over time, so 100 damage spread out over 5 second.
Fun fact: Poison damage prevents monster regen for its duration
1 Like
And does poison damage from weapons, gems etc. stack with the poison javelin?
Nah if you apply a poison that does 80 DPS then a poison that does 100 DPS, the stronger poison will overwrite the weaker one.
1 Like
If you really want to dig into the poison damage mechanics in D2, feel free to use this.
https://diablo2.diablowiki.net/Guide:Calculating_Poison_Damage_v1.10,_by_onderduiker
TLDR: It’s not that easy.
A bit rusty on my Poison overall I tbh, but afaik this would be a yes and a no.
A Poison Javelin consists of 2 effects.
1 the trail of poison gas you see.
2 the javelin itself.
1 the trail is purely skill based and does not include weapon damage so poison damage added to the weapon will not affect.
So this is No.
2 the javelin itself will also carry the poison by poison javelin, but unlike the trail it will only deal damage to the creature actually hit by the javelin and weapon damage is included in the hit, poison damage on the weapon should affect this and the duration of the poison will be converted to that of the skill used. (using Venom will always cause Poison duration to become 0,4 no matter what it was, whenever poison on the weapon is included, with iirc the exception of Poison Dagger which will overrule Venom and combined deal a lot of damage 
)
But here it would be a Yes.
This is however as I remember it, not 100% sure.
No. This is another reason there’s a fundamental game design flaw. Only the person with the highest poison damage in ur party actually does any poison damage at all. Everyone else’ poison damage is turned to 0.