When you start the fight, 2 potions appear on the table : a red and a blue one.
The red does 2% damage on the mob and takes 15% mana from the caster + it requires 108 power to cast.
The blue does 25% damage on the caster and gives 25% mana to the caster
When a red potion is cast (a long cast), the boss will aggro a lot the caster.
Make the tank cast alternatively the red then the blue potion.
If you have a regen mana, just use the red one.
When the boss speaks he puts a poison debuff on a random group member, this must be cured or it kills the player. Anyone in melee range will be power drained... healers especially should range it.