Intense Cold

Ok, here's how it works.

Keristrasza has an ability named Intense Cold that stacks on players every 2 seconds, dealing 100 damage per second.

So, to have this achievement, the players have to defeat her in heroic mode while avoind 3+ stacks of the debuff, and for that the players must always move to remove the debuff. In short, players must not stand idle for more than roughly 4-5 seconds on the same place.

I'd advise all players to use spells with a maximum cast time of 2 seconds or less ready for this boss, and spec to those abilities for the maximum DPS if needed. healers will have to probably put aside their large heals and go with flash heals of 1.5 seconds or instant spells.

The worst part on this is another of her abilities, Crystal Chains, which root the players for 10 seconds. And they'll get stacks of Intense Cold while rooted, which is BAD!

The best combination for this boss would be a tank and 3 meele DPS players always moving to left and right and a discipline priest proficient with PW:Shield and the instant heal from the Holy Tree. Paladins can also work well here, as probably they can stand still for the duration of their bubble, immune to the ability. Hunter suffer a lot on this one, as they have to keep moving. A strategic alternative would be after each steady shot, jump twice and while jumping twice, use an instant shot, like Serpent Sting or Arcane shot. Dut to this, Multi-shot should not be used in this fight.

Edit: players can remove the debuff also by jumping. This is a good tip for healers ^^ ( thanks for the info, ncoffey )

P.S.: remember that she casts a tail sweep to players behind like Onyxia, so try to dps on the sides.

2nd Edit: changed the "pet" part, according to Carebear. Thanks mate. Instead, i've added a suggestion for hunters if they are having troubles with their steady shots, since they're great part of their dps.

This is definitely an individual achievement; I was able to earn it when no one else in my group did. Also, as a reminder to druids out there, shifting breaks Crystal Chains. Not to say this is easier for a specific class or anything. (4.0.6 edit: unless you're feral, then you don't get the easy out anymore.)

For those classes that don't have many root-breaking abilities, using your pvp trinket will free you from Crystal Chains