I have been messing with these a lot as of late.
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Try putting your monsters to attack team 1 ( or ally them with any team but team 1 , sorry not sure of the exact options ) and the guards ally team 1.
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Set up a path ( only works for guards at the moment, crossing my finger for the monsters) going towards your monsters.
For ex: i have a ‘inaccessible area’ protected by pane glass in this instance and have a small infinite ongoing ambience fight going on in the background. i put about 10 guards vs 12 monsters.
pssst… Oh yeah, if anyone knows how to box out the sound of those fights though b4 i figure it out it would be a nice short cut for me thank you 
Hope thats what you meant … and yeah they get aggressive as heck and caught in an infinite loop of fightdom! lol
p.s. Also start by dropping the spawneronto terrain because the spawns do seem to stand still if the spawner is buried in the terrain a bit or if the do not spawn on solid footing ( ex: terrain tiles in the air )