Every so often he shouts and begins to channel a spell to the closest container near him. At this point, the container becomes targetable, and the party must attack it. Note that the warlord continues attacking while channeling, so the tank will still be taking damage, however, if he is not enraged his damage on any average geared tank will be negligible, so it's recommended everyone in the party starts dealing damage to the container, including the healer. It is imperative that the container be destroyed before he finishes channeling (10 seconds). If he manages to get the spell off, he enrages, increasing his attack speed by 100% and his damage by 75%. This ability will stack if more containers are not destroyed. Since they are only targetable while he's channeling, there's a certain urgency to this fight. As he will use this technique on the container close to him, a good technique to killing the containers quickly is if the tank places the boss next to each container. That way you maximize the time you have the whole group attacking the container.