Under the Crooked Tree

Quest is buggy, mob resets frequently, back to full health, repeated fears with no cooldowns, hard to solo

It's at (35,56) for anyone who are looking for the daily. And I just went there without any pre-quests during the event.

If you don't have coordinates: It's right next to the building on the hill near Bradensbrook, click for map

And as of 19/10/2016 you cannot add these witch hats to the wardrobe :-(

After accepting the quest Under the Crooked Tree (lvl 40+) from Hag of the Crooked Tree you are able to click the cauldron and phase out.
[npc=109825] appears. This elite mob scales to level and it is in a non-personal phasing, so you can see other people being on the same quest.

[spell=218660] is interruptible.

[item=139137] contains around 5x [item=33226].
Other possible items: [item=139133], [item=139134], [item=139135], [item=139136] and hallowed wands.
Although marked as "cosmetic", they are not transmoggable.
Since originally wrote of this post, the hats got a change: they are transmoggable now during [event=324].

If you're still leveling and want some EP, speak to [npc=109854] in Dalaran (neutral inn) and take his quest Beware of the Crooked Tree, which sends you to the hag.

Flight point: Bradensbrook in Val'sharah
Use the street to west coast.

/way Val'sharah 35.02 55.95 Hag of the Crooked Tree