Originally Posted by
ohmygosh
As you are an Arcane Mage, im guessing you are asking the "mini burn phases".
It's when you are at or near 100% mana, and your Evocation and Mana Gems are up. It means you can just start blowing shit up via Arcane Blast spamming, until you reach the mana needed to evocate to 100% mana back. Then starts the mana conservation phase, where you cast Blast until your gear allows, and clear the stacks with Missiles.
If you are asking for the general burn phase, it's normally when they pop Bloodlust, and you >NEED< to be with Evocation, Gems, Mirror Image and trinkets up if you want to unload hell on the boss.