Hint 1: Place these auras on the side with the others. The map gets cluttered with everything on it!
Hint 2: You'll need to position/angle the towers protecting your crystals; I didn't want to. Sorry.
Hint 3: If you're using a summoner, you can place these sets of minions at each crystal.
Hint 4: Adding these guys behind each choke point will use the rest of your SU and help against the hordes.