Toravon the Ice Watcher is the final raid boss in Vault of Archavon, and drops Tier 10 gloves and legs, as well as PvP back, feet, finger, hands, legs, neck, waist and wrist pieces. Toravon was introduced along with Arena Season 8 and the final wing of Icecrown Citadel on February 2nd, 2010.  He also drops 2x [Emblem of Frost] in both 10 and 25 man.
[Frozen Mallet]ωϖ (Heroic modeωϖ)—Attacks have a chance to apply Frostbite! Frostbite inflicts 975 to 1025 damage every 2 sec for 10 sec. If it procs, triggers...
[Frostbite]ωϖ (Heroic modeωϖ)—The Frost Bite inflicts 975 to 1025 Frost damage every 2 sec and reduces move speed by 5% for 10 sec. 1950 to 2050 on 25-player. Stacks to 100
[Frozen Orb]ωϖ (Heroic modeωϖ)—Creates a Frozen Orb at a nearby location. 2 sec cast. Summons one (three on 25-player) Frozen Orbs. Every second they're alive, they tick...
[Frozen Orb]ωϖ—The Frozen Orb inflicts 2925 to 3075 damage every 1 sec to enemies within 8 yards. Ticks...
[Frozen Orb]ωϖ 8 yd range—Inflicts 2925 to 3075 damage to enemies within 8 yards of the Frozen Orb.
[Whiteout]ωϖ (Heroic modeωϖ) 50,000 yd range—Inflicts 11213 to 11787 Frost damage to all nearby enemies and increases Frost damage taken by 25%. 2.5 sec cast. Stacks to 20. 13163-13837 on 25-player (10 sec cooldown)
[Freezing Ground]ωϖ (Heroic modeωϖ) 6 yd range—Inflicts Frost damage to nearby enemies, immobilizing them for up to 5 sec. Instant. 4625-5375 damage.
This is a fairly simple fight where the boss has 2 interesting abilities.
Firstly, he will spawn Frozen Orbs (1 in 10 man, 3 in 25) which pass through the raid, ticking AoE frost damage within a fairly wide radius. These need to be killed quickly as he will cast Whiteout soon afterwards, which does large raidwide damage. Whiteout stacks a debuff which will increases frost damage taken, so each cast imparts more damage on the raid. If the orbs are not taken down, healers will not have had a chance to top up the raid and people with damage will start dying to Whiteouts.
Melee hits from Toravon will start stacking a Frostbite debuff which adds a significant DoT to the damage taken. A 2 tank setup will need to taunt Toravon as the debuff on the other tank reaches 4 stacks, which allows time for their own to clear. At the start, tanks can handle a higher number of stacks, but as the raid gets more stacks of the Whiteout debuff it makes harder for healers to keep tanks alive. In addition, he sometimes immobilizes the tanks using Freezing Ground. This will prevent the tanks from dodging Frozen Orb.
The original advice on this raid has been to spread out to avoid multiple raid members taking hits from the frozen orbs, but this may make it harder for AoE healers to keep people up. With reasonable raid healers, the best tactic appears to be to take down the frozen orbs as soon as possible (even using melee dps if the raid is short on ranged) to allow the healers time to top up the raid before the Whiteout. If people take damage for longer by avoiding instead of DPSing the orbs, the chances of deaths on the next Whiteout increase significantly.
Healing will get more difficult as the raid gets more stacks of the whiteout debuff, but a 2 tank, 2 AoE healer, 6 dps setup in 10 man or 2 tank, 5 healer (one tank healer), 18 dps setup in 25 man has been seen to succeed.
In a nutshell
Do not stand in the way of the swirling Frozen Orbs.
Ranged DPS have to kill the Frozen Orbs immediately.
Swap tanks after 4 stacks of the debuff.
Every 38 seconds he will cast Whiteout, which does lots of Frost damage, and adds a Frost damage-increasing debuff, just like Garfrost's Permafrost. If Toravon isn't killed fast enough, the raid will wipe due to the immense amount of Frost damage taken.
Death Knights can cast Anti-Magic Shell to resist the Whiteout debuff. Since the spell has a 45 second cool down, and the boss casts Whiteout every 38 seconds, it will be applied. When he casts it for a third time, if you use Anti-Magic Shell the original debuff will be removed a few seconds later, but only if you cast the spell when he is about to finish casting Whiteout the first and third time.