Dungeons 3

This is done in the "The Storming of Dollaran" level. There are 5 Hero camps in the level but 2 of them you need to advance Crowley towards the castle gate to the North-East and take it down before you can access the last 2 camps. Be careful not to advance Crowley too far: if Crowley breaks through the 2nd gate, the level completes and you'll miss out on destroying the last 2 camps.

There's a group of Heroes guarding the 2nd gate but their aggro range is quite small so once the 1st gate is broken down you can sneak past them to attack the 2 Hero camps. The trophy pops the moment all 5 camps are destroyed.