Death Guard:
Every now and then he will switch stances , he Hass Defensive and Berserker stance ,
it depends in what stance he is for the spell that he will cast
At 25% he will unite the stances and go in to Battle Stance Will gain Armor damage , but lower AS , Will cast difrent spells again , at 10% hp he will gain 350% AS
at that point i think it will be for the best to run until 25 sec have past.
And finaly Nightmare:
A ghost boss that will cast shadow fury that damaged 300hp and Gain 50% of that damage every 10 sec in the battle , he haves a special event that will be 3 times, he will star chaneling a barn will open and u have to take the ping item click on the item to sumon the pig and comand the pig to go in to the sucrafice pit , if you dont do that in time all in the region of the boss arena will die , he does that 3-4 times , at 50% hp and 25% he gains 25 % life steal for 5 sec , in the battle will cast howl of terror and sumon undeads.