Both Dark Swarm and Disruption Web create a neutral/unowned unit. Can the player who created it be detected in a multi-player game?

-you could detect the unit's energy loss with EUDs (difficult solution, still not perfect and defilers shouldn't respawn because the unit's ID would change; mistakes when 2 swarms were casted at the same time).

-you can center a location with a defiler castrange on a dark swarm, if there is only 1 defiler allowed to cast in that region (if you have a sort of ammo system), he must have casted it.

it's the same with dweb.

The only real difference between the two is their effects, and DWeb can be moved via triggers.

There really are not many methods to stop it, but the ones there are include:

1. Using only one player/force for dark swarms or dwebs and affect units not by that player/force only.
2. Relegating two seperate players/forces to either swarms or webs, respectively, and distinguish targets based on that.
3. Physically seperating swarm/web casting players so that they cannot come within direct firing range of each other, and thus detect shot owners by the location they're in.
4. Preventing players from being able to cast altogether if within each other's firing range (setting the casting units' mana to 0 can help with that).
5. Using a turn-based system of shooting, such that only one player at a time can fire (like if they're within range of each other). You'll need to come up with your own rules for how the turns are handled, though.
6. Using EUDs to detect loss of energy, still does not work if two cast at the same time
7. Using EUDs to detect who cast it, I think it's within range of EUDs
8. Making the spell not be triggered based on who cast it, IE, have it kill anyone it hits, even allies.

Alternatively, you could constantly cycle through the defilers/corsairs such that only one has energy at a given time, but due to a fast cycle rate, the players don't have to wait too long before they're actually able to cast. It's far from being an ideal solution, though.

Ah, okay. What is a EUD?

I had resigned that it wasn't easily detectable without complex location work if dealing with more than one player. Then I played Tuxedo's Rush map that used Dark Swarm as an attack with a mineral-based ammo system. The game allowed two players, so I was hopeful there might be a way.

Sadly, what I'm doing can involve up to eight players, each with many casting units. Locations would not be feasible.

EUD = Extended unit deaths.

You can use them to get and modify (modify dosen't work anymore) extra data from star craft.

EUD means Extended Unit Deaths, it's a way of reading death counts past the actual death count table, so you read SC's memory instead.

In Rush, the second player has a Corsair, like one of the methods I mentioned, so he can tell who casts what.

Not particularly true, if you have hyper triggers you can detect the split second it was cast.

He did not say when 2 swarms were casted a split second after another, he said the same time.

Independent actions happening within a 1/8 seconds game time frame is truly a rare occasion, but it can happen.

What about this: IF it happens (P12 brings at least 2 swarms to anywhere) show an error message like "casting failed" and do nothing except removing them both.
It shouldn't happen too often when you're using hyper triggers.

Ah, I see. I was wondering that, too, but then how do all the Zerglings and Lurkers attack the second player? What keeps the Corsair player from flying over the cliffs that form the game maze?

Haven't played it 2 player but I'd assume he has centered a large location on the defiler and if the cors leaves that location he's constantly ordered/moved back.

Yeah, Nude's got it, the Corsair is just constantly following the defiler, all it is is a second gun, not a second explorer.