The sale starts on Thursday 11th of June (Today) and ends on Monday, 22nd of June.
The items available on sale are listed below:

Steam Game Packs
http://store.steampowered.com/app/338202/
http://store.steampowered.com/app/338201/
http://store.steampowered.com/app/338200/

Gold Prices up to 70% off

In-Game Items, Gold prices reduced!
All Bloodlines 60% off
All Gender Outfits 70% off
Floral, Lightning and Neptunian Weapons 60% off
Taunt Emotes 80% off
Wacky Outfits 60% off