Dungeon Siege II - Boss Encounter - Dark Wizard Triad

Fantasy game art from Dungeon Siege II.

The player first encounters the Dark Wizards in the icy Azunite Catacombs where Princess Evangeline is held in their power. There, the coven of four disperses, leaving only one to deal with the would-be heroes and rescuers. After the defeat of this lone Wizard, the remaining three Dark Wizards confront the hero together later in the story.

If you do not interrupt the initial cutscene, chances are that the script will have the Death-Magic Wizard moving into position while the other two invoke their Crystal Shields and begin summoning the very powerful energy- creature "Xzeihoranth". But if you do interrupt the cutscene by pressing ESC, all three wizards will be in place, invoke their shields, and then freeze in position while summoning and maintaining the Xzeihoranth.

If you are daring and can survive the attacks of the Xzeihoranth, a creature possibly six or more levels stronger than you, you will notice that while they maintain the Xzeihoranth the Dark Wizards take no other action. You can therefore run around destroying their crystal shields and taking them down one by one.
When one of them dies, the summon is disrupted, the Xzeihoranth thankfully disappears, the dead wizard transfers his strength to fully heal the other two, and the remaining wizards disperse to assault you with their powerful attacks.

Because their area attacks target every party member at once but can be evaded by simply running out of the visible magic-gathering area, this encounter can actually be easier if you control only one character, as you can more precisely direct that character out of the way not only of these area attacks but the powerful ground beams and short-range System Shock attacks.