Neverwinter

Edit: They finally fixed this so that you get credit simply for beating Orcus at the end of Castle Never. That makes the solution irrelevant and the achievement self explanatory. Leaving the original solution below for posterity, but just complete CN 25 times to get this.

Warning: A user below stated that he completed CN twice without getting credit, but both of those times he died during the fight and was waiting at the campire when Orcus died, so make sure you stay alive (possibly just don't release if you're perma dead) so that you get credit.

Ok I wanted to clear up some confusion around this achievement. This isn't 100% iron-clad confirmed, but I've run CN around 40 times now, and have done it with various group mixes, so I wanted to spread some info I've gleaned.

1. It requires a minimum of 5-6 million damage dealt to the boss (probably 5,but 6 to be safe). This has been confirmed in testing by Texans and Blizzard.

2. Due to #1, support classes (DC/OP/GF) are pretty much screwed right now unless you respec to high DPS. You can accomplish this by one of two means: fully respec your char to DPS, or just get a super DPS companion with bondings and the right gear. The latter is ideal, because you don't have to change your char build, but can do high damage with your at-wills. Get a Mercenary companion (comes from one of the booster packs, scourge warlock I think?). Put three Bonding Runestones in its three offensive runestone slots, preferably at least rank 10. Put a Ring of Brutality or a Ring of Rising Power +4 in one of its two ring slots, and another good offensive ring (Ring of Sudden Precision +3 or +4 from Castle Never) in its other slot. Any belt will do, so long as it has an offensive slot.

Put all Radiants and/or Brutals in the companions offensive slots on its gear. Even if you have to strip them from your character, DO IT. You get more stats over time from the companion's gift proccing than you do keeping them on your character. If you don't believe me, ask the top DPS people in the game from guilds like Asylum/LGPG/etc where their priorities were. This setup will allow you to proc much higher power (and crit if you use Brutals on the companion for the crit) in combat, allowing your at-wills to do more damage. I say at-wills because if you're a true support build, you aren't running DPS encounter powers. Personally I've seen my power proc over 100,000 and crit over 20,000 when running dailies solo. With group buffs, it gets pretty insane. From there, get a regular crew to run CN that will allow you to damage the boss a lot before they melt him.

Bubble pallies can likely get credit simply by running double bubble (two pallies in group), IF the double bubble glitch still works. If anyone can confirm this that would be super.

3. On to the fight itself. You can do this fight with two types of groups: Raw power or bubble (for now, until bubble is nerfed). We all know what a bubble setup looks like. Bubble pally properly built doesn't even need a haste cleric, but a haste cleric will help. Other than those two, three DPS classes. Group makeup two consists of a debuff cleric, a guardian fighter with into the fray, and three HIGH dps (we're talking 3500+ item level, super optimized DPS players). I've run it with as little as two super high DPS (4k item level) and one weak DPS with the guardian fighter/debuff cleric setup. If you have a super over-powered group, four high DPS and one haste/debuff cleric is enough to get the job done.

When you enter the fight, the boss will do a nearly instant-swing at the first person that reaches him. So make sure your GF or pally with bubble goes in first, or a TR/HR that is good enough to dash out of the way FAST when he starts that swing, because the animation is less than half a second. After that, ranged classes for highest chance of survival should stick to their ranged attacks. This is a double-edged sword though, because a class like the TR can throw daggers, but they don't do nearly as much dmg as duelist's flurry. Duelist's flurry is a close-up attack, leaving the TR open to those deadly swings. A GOOD guardian fighter can hold his aggro and keep him facing away from your GWF/TR types that are up-close, but not a lot of GFs currently know how to aggro-manage, as it hasn't historically been much of a thing in this game.

The death orbs don't tend to show up after players get downed (though not always), and come in the number that players were downed. Three players go down? Three orbs show up, at least in my experience. Keep this in mind, and do NOT try to revive players when orbs are around unless the orbs are on the opposite side of the room, unless you want to get one-shotted while reviving them. Scrolls of life are suddenly very handy.

Speed is the key for this fight, unless you're running perma-bubble. So if you're running without a pally and using a GF's into the fray, make sure your team coordinates the DPS classes' best power cycles with their dailies and such along with the fray and debuff from the support. Do that, and you should see huge chunks melt.

Bottom line: This fight is not a 2000 item-level fight. Good luck everyone, and I hope this info helps!

this is the last boss of castle never. to earn this, you will need to run the dungeon 25 times and beat him.

he is pretty simple, if you have a strong team, you can kill him pretty quickly. I know that he has at least three phases, though you can kill him before he gets past the second phase so there might be more.

one phase, he will disappear and you have to prevent minions from entering the green death sphere. succeed and he will return.

another will have death spheres float around while he fights.

the final is closing rifts to prevent him from getting stronger.

it should be noted that the phases are a bit random.

Don't know if there are more, but if you have the DPS, you can take him out before he activates the death spheres.

one added note, The tracker in the game journal might be a bit glitchy or the achievement requires you to land the killing blow. I have fought him at least 12 times, as of this note, and only have 4 of 25 in the journal.

I am hoping that it is just glitched for tracking or else this achievement will be incredibly unfair for support classes such as DC or tanks.