They have a energy-ball attack (it hits a big area) that seems to deal more damage when players are standing closer. So, its recommended that players stand far from each other.
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They also have a parry-attack (when you attack the boss, it will trigger the attack, so you will receive damage).
The parry attack seems to be Holy damage and it goes from 800-950. So, avoid area spells! Because if you trigger the parry attack on multiple prospectors, chances are you will die.