Listen up, all you hardworking collectors! From Thursday, 14th December 2017, you can collect letters and convert them into fantastic rewards!

The ancient mighty phoenix skills give you the passive effects Blazing Aura and Phoenix Avatar, which has a chance to increase your Crit Power against monsters by 2 times for 6 seconds, as well as revive you once every hour!
Letters
Between 14th December and 9th January 2018 (5 AM), every player who logs into TERA will receive the following item after completing a Vanguard Initiative Quest: [Event] Veteran Fire Demon's Tome. This item can be opened by right-clicking and contains one of 18 letters at random.
The Veteran Fire Demon's Tome can also be earned as loot in dungeons:
- Thursday, 14th December (15 AM) to Tuesday, 9th January 2018 (5 AM)
- RK-9 Kennel (Hard)
- Lilith’s Keep (Hard)
- Broken Prison
You can also pick up tradeable versions of the [Event] Fire Demon's Tome item in the TERA Shop, containing the same letters.
Runestones
From the Merchant in Highwatch you can buy various different runestones, which can be used to convert specific combinations of letters into a reward.
For example:
The “[Event] Runestone: B, G, M” item can only be used if you have the required letters B, G and M in your inventory. Using the runestone will combine it with the three letters and convert them into a Phoenix Skill as well as 50 Emerald & more!
Ten copies of the same letter can also be converted into a new [Event] Veteran Fire Demon's Tome.
Reward Details: Link