Things to get before starting the event:
18000 gold, pure silver ore which you can mine off silver veins or buy it off the auction house (its tradeable)


To begin the quest you need a "melted snowflake" from one of the unusual snowflakes outside Orgrimmar,they are just bellow the little lake around the pvp training dummies.For the alliance they are directly south of the gate that leads into stormwind
   For the horde side- when you have the item go to Silvermoon and talk to Inethraveen in Sunfury Spire by taking the silvermoon portal, npc will be right behind you.
   For the alliance side- Mari Methborn in Ironforge, Mystic ward directly left of you when you take the portal to Ironforge.
Going through all of their dialogue will give you the first quest. You cannot talk and get the dialogue for the first quest without getting the melted snowflake from unusual snowflakes first.

For the first quest you need to gather clues by talking to innkeepers around the world.
1st clue is in Uldum, Ramkahen
2nd clue is in northern barrens, Ratchet (6000 gold needed)
3rd clue is in booty bay (6000 gold)
4th clue is in hyjal, Nordrassil
5th clue is in eastern plaguelands, light's hope chappel
6th clue is in deepholm
7th clue is in winterspring, everlook (6000 gold)
(order at which you get clues doesn't matter)
You do not turn this quest in at the NPC in Silvermoon/Ironforge but at Thrall who is in a ruined house in the blasted lands: http://i.imgur.com/bbS80KR.jpg

The next quest requires you to kill Unusual Snowflakes in this area for the "perfect snowflake": http://i.imgur.com/uNqARGF.jpg
The item is 15% drop chance and the mobs have a 7 minute respawn timer. Will need to be rolled for if in a group.
Turn the quest back at Thrall in blasted lands.

Next you need to go to winterspring and find a dwarf named Ann Nimocs. If she is attackable melee her once to be able to speak with her. When you talk to her she will give you a 2minute duration debuff 'On fire'. You NEED this debuff to be able to finish the quest.
Find Annie which is in a cave east of Everlook. She is in the north part of the cave. If you lose the debuff talk to the dwarf again to get it.
Talk to her and unfreeze her.
Locations of both the dwarf and Annie: http://i.imgur.com/w9FozFl.jpg

Next quest is in dragonblight and you need to find Elise standing near the edge of the cliff here: http://i.imgur.com/UKt68sb.jpg
Her respawn timer is ~7 minutes, wait for her to respawn and talk to her to trigger the event. Annie will show up and Elise will freeze her and turn hostile. Damage her down to ~60% hp and she will freeze you before jumping off the cliff. Wait till Annie unfreezes you.
Turn the quest in at the base level of wyrmrest temple where she will offer you 2 quests:

First quest is to get the "pure silver ore"
Sindragosa's claw, drops from Sindragosa in ICC any difficulty
and Alodi's essence which you get from the second quest

Second quest takes place in Karazhan:
The quest NPC where you turn it in is just inside the main entrance in front of the butler.
Kill Moroes for the journal.
Kill Prince Malchezzar for the Dimensional Essence Container.
Turn the quest in at the NPC near the entrance, next quest will spawn alodi and finishing the quest at him once he is done talking will reward you with his essence. If he despawns before you finish the quest just abandon it and take it again.

The last quest requires you to fight Elise in the hour of twilight dungeon in the caverns of time. She is behind the first boss and talking to Annie will start the fight. Only try and solo this if you have a lot of selfhealing.
You can fight the first boss until Thrall buffs you with bloodlust and then start the annie fight, will make it a lot easier.
Go in her melee range to start the fight and do not go too far away from her or you will die!
Avoid the frozen orbs flying around, they will freeze you and deal damage.
The small hp elemental is harmless and just casts some small damage spell, the high HP elemental deals decent melee damage and the unattackable elemental deals a lot of melee dmg but is slow and has to be kited. It will die on its own after some time.
When you dps the big elemental to 15% hp will freeze everyone and do 60%/70% of your max hp as dmg! If you do not have full hp here you will die since he will stun you and keep meleeing you as well.
After you kill the elemental you just fight with Elise until she reaches 50% hp and you can finish the quest.

Reward is 30k gold,the tabard,guaranteed blizzard bear mount and 1 random other item from the bag