Rise of the Witch King

This sounds like a bug . Shouldn't Darkness always cancel someone else's Darkness normally? There is no such thing as "same time" with computers. Something always happens before something else even if both players had clicked the button at the same time. So if we have two Darkness FXs on opposite teams going on at once, we have a problem.

Yeah but games works on "ticks" (~30 ms in RotWK). Using something in exactly same tick is nearly impossible so lets treat it as ester egg not as bug ^^

I knew the double darkness happened in this game before making a cast and still didn't notice it while casting XD. It did indeed happen though. Weird

If it's just the FX then it's not such a big deal (seeing as this doesn't happen often). However, if this includes the attribute modifiers, then we indeed do have a big problem.