The encounter consists of one phase. The 10 minute enrage timer is generous and should not be of any consequence. Three tanks are required, one of them can be a ranged tank (e.g. Warlock).
At all times, one of the three princes has Invocation of Blood. The two without the buff have 1 HP and cannot be damaged, only the buffed prince has a proper health score and can take damage.
Invocation of blood always starts on Prince Valanar (middle), and switches randomly every 30 seconds to another prince.
All three princes have rather low armor and thus take high melee damage. DPS cooldowns should be used on Keleseth, if the tank has sufficient threat, since he frequently casts Shadow Lance which makes it impossible for him to dodge.
This prince can basically be tanked by any class with a ranged attack. He does not use any melee abilities, he instead spams …”