Multiple quantum flares, multiple krionus virus traps. Everything negative can stack and subsequently destroy a stat.

I don't think so, as I once got hit 5 times by a Stryll Traper's effect and it only applied once.

Dan would've posted if this was pat of an update, but he hasn't.

Are you sure it's not the multiple-bonus display bug, Spoony? Sometimes the game displays the same bonus/effect multiple times, but only one of them is actually applied. It's happened to me before now several times, and i've actually posted a thread about it.

The quantum flare seems to be the only significant thing that negatively stacks. You can use two to get -75% scan and 3 for -87.5% scan and so on. The -90% attack from a krionus trap isn't very different from the -99% of two.

I've had it from non-artifact effects too, like the special effects some boss NPC's can cause. That's mainly what i was referring to earlier.

Firewalls are doing this too, I hit one and I got the effect of two. And not that it said two but it actually had the effect of 2 of them.

Well then you must have used a dark pyramid to get the 2nd one. Someone used multiple EMP spheres on me, but I didn't check to see if they stacked though.

Nope I just hacked a guy once, I then went from 500+ cloaking to 0, which can only happen when you get -99%+-99% again.

You can always get 50 cloaking from a pyramid. That got changed like a month ago. I'm startng to think it was all changed back then and we just haven't noticed it until now. I want to use 5 EMP spheres on someone to see if it stacks.

Actually dark pyramids dont make a cloaking when you're firewalled. I know, I've tried.

It has for me for the last month or more. Only 50 cloak, but it can still make hacking possible through a firewall.

hmm.... It may be that effects stack in order of use. It may be if you use the dark pyramid before the firewall it goes to 0 but if you use it after it goes to 50.

Yeah, you can spring 2 firewalls that way. but you can only have 1 dark pyramid active, so its a one time deal every 10 hours... or however long a dark pyramid lasts.

I have a feeling EMP spheres stack consecutively also. 1=10%, 2=19%, 3=27% off of their defense.
It would be a great way to help assassinate some higher level more efficiently.

Then I'm guessing percentage based effects stack, then neumeral effects don't? or is it an artifact-by-artifact basis?

Well when you use artifacts on yourself, you can only have 1 active of the same thing. All the artifacts you can use on others seem to be percentages that stack consecutively... those and trap effects. I don't think there are any numerical offensive artifacts.