To get the rewards you need Burning Blossoms. Which can be obtained trough a number of quests, some daily quests in your city or diminishing the bonfires of your opposing faction.
Keep in mind each bonfire can only be extinguished once a year.
Wowwiki's info on the item is rather limited, so I figured I'd make a post for the regular blog readers. OK, maybe more for myself since I couldn't be arsed to sort trough the thing manually, and wanted an alphabetic list, but the other option sounds nicer don't you think? Hopefully you find this list useful.
Some credits go the comments section on wowhead for the original (poorly sorted list) of Burning Blossoms.
Opposing faction gives an item for 25 tokens, own faction doesn't seem to work other than daily quests. H = Horde, A = Alliance, but I figure you're smart enough to understand that.
Own faction awards 5, opposing faction awards 10.
Thlop on the Official forums also posted a nice map, as seen on the right.
On top of 5-10 Burning Blossoms, you also receive up to 5g 95s - 11g 99s at level 70 (or XP if not maxed yet)
You'll notice a few NPCs in shat, org or uc, etc that give you a quest to direct you to the fire masters. Each of these 2 quests give 1 blossom. Once there you get a few more quests :
Torch Tossing : 5
Torch Catching : 5
More Torch Tossing (daily) : 5
More Torch Catching (daily) : 5
Incense for the Festival Scorchlings : 1
PS : Torch catching SUCKS BADLY!! Don't try to do this quest when it's crowded near the bonfire.
Also a chain which sends you to the Zoram Strand in Ashenvale. Starting with :
After this he'll give you two quests, Striking Back (Daily) which will be a different quest based on your level, and awards 10 blossoms. And Ahune the Frost Lord which will allow you to summon the boss on Slave Pens normal mode. (Heroic needs no quest)
Lord Ahune will drop a Shard of Ahune when killed, the item is lootable by everyone in the party. The boss can be summoned once a day by each player, he only drops the quest item once a year though. As by default, you can only kill him once a day on heroic mode.
Lord Ahune can drop some ilvl 110 epic items. Mostly cloaks on normal, necklaces and cloaks on heroic. Deathfrost enchant drops both on normal and heroic, as does the pet.
The boss is fairly straightforward, like most seasonal bosses. It's a two phase fight, and he will continue to switch between these two phases until death. Clear the mob packs as you enter, left and right of the cave passage, and the bogstroks near the water. Make sure you stay on the left as the boss does have some knockback attacks.
Summon the boss by clicking the left pillar of ice and he will spawn on the right side a bit further into the cave. Phase one starts and the boss will summon a constant stream of mobs. Tank the large earth elemental and finish it off fast. Don't bother doing much DPS on the boss in this phase as he only receives about 25% of the normal value. Do not melee him, as he'll knock you back, and deal about 3-4K frost damage. The boss is immune to frost.
After about a minute he'll "retreat" and his frozen core is revealed. You now have about 30 seconds to DPS him down. If you don't have full T6 and crazy DPS you will probably need to repeat this process once or twice.
I'm not sure what blizzard's exact intention was with the fight, but we've had the boss bug out on us in two different ways: We killed him when he was in phase 1 again after submerging, and dropped no loot for us. When we started the fight again afterwards, he would submerge but not reveal his core, thus we could not DPS him in phase 2. Make sure you reset the instance after each kill, just so you're warned.