Harpies will flock to a full gold mine! "Screeching Canyon? Why do they call it... oh."
Keep anti-air (preferably AoE) to counter Harpies that spawn on gold veins that have 3 gold. Adding a Dark Iron Miner can help take all the gold on the map from the enemy.
For every PvE mission, there is a campaign version and a Heroic version. When you first begin the game, you can only participate in campaign missions. Upon collecting 50 sigils, you will then unlock Heroic missions.
Campaign missions will grant rewards after the first successful clear with ANY family. Heroic missions must be completed with EACH of the 5 different families in order to receive the mission rewards.