Summer Sale 20th of July - 3rd of August (11:59pm GMT +1).
Unlimited Realm:
20% Discount at the website store for Twilight and Devilish sets.
20% Discount for BoP Weapons (Rank VI) at the Summer Sale vendor.

The Mystic Grounds:
20% Discount on Season 15 (Prideful), Tier 16 Sets (SoO) and Tier 15 (Throne of Thunder) at the website store and ingame vendor.