[This should now be pretty accurate for Live! Thanks to my fellow raiders for their input from other perspectives. I’ve also added heroic information from Paragon’s video, although we stuck to normal for this week so I have no direct experience]

I’ll do the three Lieutenants first, since they can be done fairly quickly. The main Halion strat is below.

Halion’s Lieutenants

Baltharus the Warborn – East

This fight is a fairly simply one, requiring a main tank and two (1 on 10-man) add tanks. At 70% and 35% HP (only 50% on 10-man) Baltharus will summon a clone of himself with the same HP as he has. These clones should be simple picked up and off-tanked, being careful to move them out and face them away because unlike Baltharus they cleave, and they also do Blade Tempest like he does (see below). The clones will despawn when Baltharus dies, so there’s no need to DPS them.

4 seconds before he clones himself he will cast Repelling Wave, knocking nearby players back and dealing fire damage to them, so watch your position relative to nearby trash or run out when a clone event is due.

The other abilities associated with Baltharus are a 15-yard range frontal cone attack hitting every 0.5s (Blade Tempest) which melee need to move away from and healers need to be aware of, and Enervating Brand, which stacks a debuff reducing the damage of the target and players within 12 yards of them by 2% per stack, and increasing Baltharus’ damage by the same amount through the buff Siphoned Might. This is simple enough to avoid by making sure the ranged are well-spread at all times, and keeping away from the player with the Brand.

General Zarithrian – South

General Zarithrian is a tank-swapping fight with adds which need to be nuked down. 2 or 3 tanks will be needed.

The tank swapping is due to the stacking armor reduction debuff (Cleave Armor) placed on his tank which reduces armour by 20% per stack and lasting 30 seconds. Tanks should therefore swap roughly every 3-4 stacks, depending on the timing, your healers and your gear levels.

Zarithrian will also spawn adds at either side of him (one each side on 10-man, two each side on 25-man), which should be picked up immediately and DPS’d down quickly before switching back to him. On 10-man these can be “tanked” by melee DPS, on 25-man off-tanks can be used.

Finally, General Zarithrian also has an Intimidating Roar, fearing everyone within 40 yards for 4 seconds (not magically dispellable, although Tremor Totem and Beserking do work). Fear Wards on tanks are very useful here, since he will apparently chase unfeared people as a priority.

Saviana Ragefire – West

This appears to be a single-tank fight. Saviana should be faced away from the raid, because she has a Flame Breath which she uses roughly every 35-45 seconds, hitting for 39,000 fire damage (28,000 on 10-man).

She will also periodically Enrage, which can be Tranq Shotted or Anaesthetised as usual.

The main ability of Saviana’s that the raid need to watch out for is the air phase. She will fly into the air and mark 3 random players with Flame Beacon. After 5 seconds the Beaconed players, and anyone else within 10 yards of them, will be afflicted with Conflagration, dealing 9000 fire damage per second to those directly affected, and 2,500 fire damage per second to anyone else within 8 yards of them, and also disorientating them for 5 seconds. (Essentially this is another Vile Gas mechanic, with elements of the Frost Beacon on Sindragosa).
This should be easily countered by staying spread out and by keeping away from anyone with a Flame Beacon, and having a designated area for Flame Beacons to run to and spread out (like Sindragosa again). We chose the water for this.

Halion the Twilight Destroyer

Tanking: Two tanks: one for the Physical realm, one for the Twilight realm.
In lieu of the Chill of the Throne debuff, Halion has Twilight Precision which increases his chance to hit by 5% and reduces your chance to dodge his attacks by 20%.

Healing: I’d recommend 3 healers on 10-man, and 6-7 on 25-man (normal mode), since the enrage timer is quite generous and the damage can be fairly high, especially in the Twilight Realm where there is a raid-wide damage aura (Dark Shroud).

Buffs: Fire Resistance and Shadow Resistance would be useful for the Physical and Shadow realms respectively.
Magic or Curse removal is vital in both realms. Body and Soul may also prove valuable, especially on Heroic.

Key Debuffs: Fiery Combustion/Soul Consumption

Bloodlust: Most likely pop BL at the start of Phase 2 because it will help with the raid-wide damage aura. A potential alternative might be at 51% when everyone is together before the raid splits in half for Phase 3, although it will probably be partly wasted due to the movement and taking the portals. The optimal time will probably depend on the timing: whether pot, trinket and other cooldowns are ready in Phase 2 or not until closer to the start of Phase 3.

HP: 25-man: 45,300,000 (normal), 58,600,000 (heroic)
10-man: 11,800,000 (normal), 15,339,900 (heroic)

Enrage:

Video: EffBieEi (PTR, normal) Paragon (Live 25-heroic)

Halion is a three phase fight in two different realms, transitioning at 75% and 50%.

Phase 1 – Physical Realm

When you engage Halion, he will create a ring of fire around him (the location is visible as a bare circle in the grass). Once this is done he should be positioned near the edge of the available space to give the raid room to run away from the various abilities. Ranged should initially stand near one edge of the room, to keep Meteor Strike fire trails out of the way.

Halion has a Flame Breath, hitting for 30,000 fire damage (20,000 on 10-man), a Cleave which will likely kill non-tanks, and a Tail Swipe which does not knockback but does stun, so avoid the front and the back.

There are two key abilities to respond to in the Physical Realm. The simplest is Meteor Strike. A random player is targeted (an orange rune and Hellfire effect mark the strike zone) and roughly 5 seconds later a Meteor lands on that location, dealing 20,000 fire damage to everyone within 12 yards and shooting out lines of fire in a cross pattern, lasting roughly 25 seconds. The raid should be alert for this and run away from the landing spot immediately.

The second ability is Fiery Combustion, cast on a random player every 25 seconds (20s on heroic), making them appear to be on fire. This debuff ticks for 4,000 fire damage every 2 seconds, and every tick stacks Mark of Combustion on the victim. When this debuff is dispelled by magic or curse removal, the player drops a fire patch, the size of which is proportional to the number of Marks of Combustion they had, and which will damage peple within it and knock people back if they are too close when it spawns.
Anyone getting Fiery Combustion should run out of the raid quickly (like XT-hardmode) and be dispelled, then rejoin the raid. A dedicated dispeller would be very useful to make sure these are left in convenient places. The back or edge of the room would be favourite.
The fire patch will last for roughly 40 seconds.

Phase 2 will begin at 75%.

Phase 2 – Twilight Realm

Halion will go immune and open a portal to the Twilight Realm in the middle of the room. The entire raid except the MT and a healer (or two) should take this portal.

The Twilight tank should position Halion in the middle of the room, because of a couple of different abilities, although Halion will still Breath the tank (with Dark Breath instead of Flame Breath), so the raid should be careful of their position. He will not conserve aggro from Phase 1, so the tank will need to be quick and DPS should be careful not to grab aggro too early.

In place of Fiery Combustion is the new ability Soul Consumption, which stacks Mark of Consumption, and leaves a shadowy void zone in place of a fiery patch when dispelled (magic and curse). The void zone will suck players to its centre when it spawns, as opposed to the fiery patch which punts people out.

There is no Meteor in this phase, instead Halion summons two Shadow Orbs which will orbit the room on opposite sides, looking like Dark Nuclei (from the Blood Princes encounter). For part of the time (10 seconds on, 20 seconds off) they will cast Twilight Cutter, creating a beam between them which will deal 15,000 shadow damage per second to people caught in it. The raid will need to move out of the way of the beam, and be wary of their position when it is due to start up (you get an emote: “The orbiting spheres pulse with dark energy”, after which you have 5 seconds to get into a good position). During the beam phase the orbs will move around roughly 25% of the room.

When the Cutter is active, the tank in this Realm should rotate Halion clockwise (the direction the Orbs are moving) so that the raid is able to stay to Halion’s side(s), with the beam at 45° to the line of Halion’s body and passing through the centre of Halion.
There’s a trick here which is easy to miss: the timing is such that where the Cutter is when it ends is where it will be when it restarts, so if the tank stops rotating Halion immediately when the Cutter ends, everyone should automatically be in position ready for the next Cutter. You may need to make small adjustments as required by your positioning and how quickly you can stop moving.

In addition, the Twilight Realm includes a raid-wide Shadow damage aura called Dark Shroud which deals 3,000 shadow damage every 2 seconds to the raid members in this Realm.

At 50% Halion will transition to phase 3. There is no aggro drop for the tank in the Twilight Realm, but the tank in the Physical Realm will need to pick him up again.

Phase 3 – Split

At 50% Halion will open a pair of portals in each of the realms, one at the East side of the room and one at the West, allowing movement between the Realms, and loses his immunity in both realms. Half of the raid should move up to the Physical Realm, leaving the other half in the Twilight realm. You want roughly equal DPS, because of the Corporeality mechanic, and melee are probably best in the Twilight Realm due to the increased movement in this phase and their tendency to group for AoE heals, although ranged may find it easier to see and avoid the Cutter, so select the split as appropriate for your raid team.
Because of the aura in the Twilight Realm, it will probably be worth assigning extra healing to this Realm.

The first thing to say is that you should pause DPS in the Twilight Realm briefly to allow DPS to get into the Physical Realm and get established. It is possible to push Halion’s corporeality quickly in one direction while the transition is happening, leading to a gibbed Physical Realm tank.

At the top of the screen (where the attempts counter lives) you will see an indicator for Halion’s Corporeality. As you DPS his physical form he will retreat into the Twilight realm further, losing Corporeality but doing (and taking) more damage in the Twilight realm and doing (and taking) less damage in the Physical Realm. And of course the inverse is true.
Therefore the goal is to keep his Corporeality as close to 50% as possible, making small adjustments by moving a player or two between realms as needed.
Remember, the more corporeal he is, the more damage he takes and does in the Physical Realm, and vice versa. If he moves too far in either direction, he will heal to full.

Heroic

• Halion’s health and damage are increased
• The size of the fire and shadow patches is increased, requiring quicker movement. Body and Soul may prove invaluable
• The cooldown on the fire and shadow patch debuff is 20s, down from 25s on normal
• In the Physical Realm the Meteor (and associated fire trails) also spawn adds: 10-12 Living Embers from along the fire trails and a Living Inferno from the impact site. The Inferno appears to need a tank, while the Embers may be melee-tankable
• In the Twilight Realm there are now 4 Shadow Orbs instead of two, meaning that there are two crossed beams to avoid; they also orbit quite a bit faster. This means the tank’s rotation of the boss needs to be much smoother as the space available will be much smaller, and people will need to anticipate their position
• The shadow patch also applies a movement slow, so Hand of Freedom or Body and Soul is quite helpful to get the person out of harm’s way
• In Phase 3 the fire and shadow patches appear to affect both realms. The explosion appears to be limited to one Realm only, just the ground effect crosses the Realms (untested)

While the fight and your strategy shouldn’t change enormously going from normal to heroic, there will be a lot less margin for error.

In the Physical Realm the adds will need to be picked up, and the Inferno DPS’d down (perhaps by ranged only while melee cleave the Embers down while DPSing the boss), and this is the only significant difference except a need for increased speed to stop the fire patches being dispelled too late and getting too large.

In the Twilight Realm the additional beam means that players need to be careful to take up a position behind one of the beams and follow it fairly closely, and the tank will need to turn the boss in a smooth motion: too slow and the tank will be hit by the Cutter, too fast and the DPS may be hit by the tail, stunned, and caught by the Cutter. If you have the hang of the movement in normal, then heroic should not prove too much more difficult.

Once you reach Phase 3, your space for running out becomes much more limited because you have, effectively, twice as many fire/shadow patches to avoid. Careful placement may help, such as working around the room in one sense (clockwise/anticlockwise) Grobbulous-style, rather than placing them randomly.