Diablo III Encounters System Detailed, Screenshots

Blizzard's official Diablo III website has been updated with information about the behaviors and tactics that creatures will utilize when we're attempting to cut a path through them in the action RPG sequel. We also learn about some new monster types:
...when you first see the unnerving Vessels -- human cultists who've given their bodies over to demonic possession -- you'll notice that they stand numbly in place, tapping their staves on the ground and seemingly ignoring you. Yet that doesn't mean that you can ignore them. Within an indefinite amount of time, the monstrosities possessing the Vessels will tear through the flesh of their living hosts and emerge onto the battlefield, utterly consumed by rage and hell-bent on inflicting grievous harm. When encountering untransformed Vessels, it's in your best interest to kill them as fast as possible -- but trying to accomplish this can put you in the center of a melee, or take your focus off of other targets who'll savage you in the meantime. It may not seem very heroic to kill first and ask questions later, but the fate of Sanctuary is at stake - and demon-slaying is not for the faint of heart.

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"Frenzied" monsters enter a temporary state where their damage, hit points, defense, or other attributes are increased. It's in your best interest to avoid engaging them while they're frenzied -- but they also pose a greater threat in this state, meaning that if they're left unchecked, they can dish out swift, fatal blows. As you grow increasingly familiar with the timing and scope of straightforward behaviors, you'll learn to avoid and counter them -- only to run into new, increasingly complex monsters as you progress through Diablo III's acts.
Nine new screenshots that help illustrate the text are also available for your viewing pleasure.