The description, make it seem useless as a proc, as it shows extremely weak dmg, not indicating if it is a dot effect with ticks of dmg or 1 tick is all you get, the stacking makes sense, but stacking weak single dmg effects is pointless!!!
I think the way it works is if you trigger a proc on a target, the one-time immediate damage is: listed_damage*number of stacks currently applied to the target. So if you build up 5 stacks on a target then a weapon procs on it, it would do 5 times the listed damage.
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It procs when exactly? Every second? Every 3 seconds? When it reaches 5 stacks? When the stacks wear off?(this one would be absolutely stupid)
The point is, the description does not say.
The first thing I thought of when I saw one was the disruptors from DS9.
Praetor of the -RTS- Romulan Tal Shiar fleet!