Hour of Twilight is chronologically the last of the three new 5-man dungeons in patch 4.3. However, both it and End Time have been available for far longer than Well of Eternity, so most of us have wound up having a lot more experience with the former than the latter.
As with our other guides, I've continued to include the new Explain it in 5 seconds or less feature, for all those glue-sniffing players you'll encounter through the Dungeon Finder. Have fun with them!
As with End Time, you'll find yourself talking to Nozdormu at the start of the dungeon, and you'll take a little time portal to the beginning of the instance. Talk to Thrall, and Hour of Twilight will begin. He'll accompany you for the rest of the dungeon. Initial trash isn't anything to worry about, and your first hurdle will be Arcurion.
This is definitely not a tough fight and should be considered a warm-up for Asira and Benedictus. If your group has trouble surviving this, it's only going to get worse.
Explain Arcurion in 5 seconds or less Interrupt Hand of Frost, kill Ice Tombs, and stay out of bad.
Icy Boulder Adds will appear on the cliffs lining the canyon and toss boulders at you. Where they'll land is marked on the ground with a frost circle, so you'll have advance warning and can run out.
Icy Tomb When the fight starts, Thrall will concern himself with keeping the adds on the cliffs under control. Arcurion will get tired of this and eventually freeze him in an ice block. You'll need to kill this and free him, or the adds will overwhelm the group.
Hand of Frost You'll see this cast by Arcurion himself, and pretty constantly. It's a ton of single-target frost damage, but it's interruptable. This should be a priority, because healing through this gets expensive fast.
Torrent of Frost When Arcurion's health reaches 30%, he stops what he's doing, levitates, and starts to channel Torrent of Frost, causing uninterruptable frost damage to everyone in the group. Thrall will respond by casting Bloodlust. While the damage isn't overwhelming, it's relentless, and he'll have to die.
Tanks Your primary concern here will be interrupting Hand of Frost, and you'll need help to get all of them. Otherwise, keep an eye out for frost circles spawning under or nearby Arcurion while you're tanking him, or you're likely to get both yourself and your melee hurt by a boulder.
DPS Help the tank interrupt Hand of Frost, get Thrall out of the Icy Tombs, and stay out bad stuff. Really, that's about it. Save your cooldowns for 30%. If you're a mage or a shaman, using Time Warp/Bloodlust at the start of the fight gives you the benefit of two haste buffs over the fight, as Exhausted/Sated is unaffected by Thrall's Bloodlust.
Healers This is an ugly fight to heal if nobody can find an interrupt button, and if you're in a PUG, you should probably count on having to heal through a few. Damage isn't otherwise bad. People getting hit by boulders will take about 15-20K damage a pop.
You'll find yourself at the top of Galakrond's pit for the start of the next trash clear. Trash before Asira is pretty nasty, to the point that you might want to let Thrall tank a mob or two on his own. While you can attempt to crowd-control a few, he's pretty likely to break it. Interrupt the mobs' Mind Flay ability as much as you can as the damage is huge.
Asira has a few fairly annoying abilities. Fortunately, what she doesn't have is a lot of health.
Explain Asira in 5 seconds or less Stay out of Smoke Bomb and on top of the light circles that Thrall's totems provide. If you're a caster, try to keep the tank or Thrall standing between yourself and Asira.
Mark of Silence As far as I know, this will be automatically applied to anyone with a mana bar and there's nothing you can do to avoid it. It's not a problem in itself, but it becomes one once Asira starts throwing knives (which, I might add, she will do with great frequency).
Throw Knife This ability will be the bane of your casters' existence. She can toss multiple knives at the same time, and when it hits someone with Mark of Silence, it silences them for several second in addition to causing some minor damage. If your casters and healer can't find a way to avoid this, they will spend most of the fight unable to cast. On the plus side, keeping another player (or Thrall) between you and Asira will (usually) prevent her from hitting you with a knife.
Choking Smoke Bomb This is similar to the rogue's Smoke Bomb ability and will prevent anyone from healing you or casting at Asira while you're in it.
Thrall's totems Thrall will toss down fire totems that put golden circles on the ground. While you're standing on these, you get a health and damage buff that stacks. It's worth your time to continue moving to new totems, as the effect stacks but the totems don't last forever.
Blade Barrier As if Asira's mechanics weren't annoying enough, at low health she puts up a barrier that reduces all damage
Tanks Move her out of Smoke Bombs immediately -- you can't be healed within them, and don't forget that they also LoS you from your healer. You may or may not want to keep moving Asira on top of the new fire totems, as the Smoke Bombs she drops will periodically force everyone off the totem's buff circles. Otherwise, I was told by a tank in this instance that placing yourself between Asira and your healer will keep her from throwing knives at him/her. I tried this, and while it doesn't seem to be completely foolproof, it does seem to work most of the time and will turn Asira's most irritating mechanic into a non-issue.
DPS As with tanks, stay out of Smoke Bombs if you're melee. If you're ranged, park yourself on top of the circle of light given by Thrall's fire totems and resign yourself to the quite-likely possibility that, unless you're a hunter, you're going to spend most of this fight silenced.
Healers This fight can be annoying. If your tank's dancing around like a ferret on meth and you can't keep him/her between yourself and Asira, rely on your instants and HoTs (should you have them), and use your bigger heals in the moments you're able to cast. There's actually not a lot of damage on this fight, but you have to pick and choose what your heals are going to be as carefully as possible.
After Asira's dead, you'll hop on a few red drakes, which will take you to the next series of trash pulls. Trash preceding Benedictus looks a little chaotic, but it's actually not bad. You'll need to down a series of skinny tentacles popping out of the ground and some spawning mobs, most of which will make an inevitable beeline for your healer. However, none of them hit very hard.
Benedictus himself is a different story and is a two-phase fight. However, his mechanics are pretty much the same in both phases.
Explain Benedictus in 5 seconds or less Spread out, dispel Righteous Shear/Twilight Shear, interrupt Smite/Twilight Blast, and stay out of waves.
Smite Interruptable. It's a decent chunk of damage, and your healer will hate you if you don't prevent it.
Purifying Light Benedictus will channel a lengthy spell that sends three orbs to damage a nearby player. Uninterruptable and unavoidable.
Righteous Shear This is why you'll want to spread out. Righteous Shear actually isn't a cast ability but rather a debuff that stacks to two and then causes damage (a lot of damage) to the target and anyone nearby. Both stacks need to be dispelled as quickly as possible.
Wave of Virtue Periodically Benedictus will summon a wave that sweeps across the platform in a random direction. In phase 1, you can avoid it by either running away or standing under the Water Shell that Thrall provides. In phase 2, you'll just have to avoid it.
Thrall In phase 1, Thrall will help out with Cleanse Spirit, Chain Lightning, and (most importantly) Water Shell. While healing, I found Cleanse Spirit to be pretty unreliable; you'll spend more time and mana waiting for Thrall to take a stack off Righteous Shear than you'll spend just doing it yourself. However, Water Shell, and Chain Lightning are definitely helpful. Standing under Water Shell doubles your damage and makes you immune to Wave of Virtue. In phase 2, Thrall is incapacitated and unable to help at all, so you're on your own.
Phase 2 In phase 2, Benedictus reveals his dark form, and you lose Thrall's help. However, all of his abilities are simply dark versions of the ones he's already got (for example, Corrupting Twilight instead of Purifying Light, Twilight Blast instead of Smite, Twilight Shear instead of Righteous Shear, Wave of Twilight instead of Wave of Virtue), so you should treat them the same way.
Tanks As long as you can interrupt Smite/Twilight Blast and stay out of Waves, this isn't a tough fight to tank. Sadly, that's mostly because you're not really able to affect the more dangerous mechanics. Your healer is going to be occupied with a lot of random damage and dispels on this fight, so blow cooldowns preemptively.
DPS If you have the ability to help dispel Righteous Shear, you might want to help healers whose mana is running low. Otherwise, don't get hit by waves, help the tank with interrupts, and save your cooldowns for sub-60% (which is when Benedictus starts phase 2).
Healers This fight is mostly on you. The healing load on this fight varies a lot by group skill and the number of interrupts used. You are likely to expend a lot of mana dispelling Righteous Shear and a lot of mana healing through the random damage from Purifying Light/Corrupting Twilight. However, if the group is good about interrupting and staying out of waves, Benedictus' damage is otherwise negligible. Brace yourselves for what could be some of most exciting updates to the game recently with patch 4.3. Review the official patch notes, and then dig into what's ahead: new item storage options, cross-realm raiding, cosmetic armor skinning and your chance to battle the mighty Deathwing -- from astride his back!