Codex: Harlequins contains a wealth of background material and rules - a must-read for Harlequins collectors.

The 80-page hardcover book contains:

• The Harlequins' tale of the tragic fall of the Aeldari and the Harlequins' homage to the charlatan god Cegorach, who escaped the fate of the other gods and thus saved his followers from the sinister pursuit of Slaanesh
• Weapons of the Deadly Art: An overview of the varied and deadly weapons and equipment of the Harlequins
• The Big Stage: A map of the galaxy showing the locations of Craftworlds, Web of a Thousand Gates portals, Exodite worlds, and other planets important to the Harlequins—both Imperial and Necron worlds
• The Black Library: A description of this infamous realm within the Web of a Thousand Gates, where the sum total of all Aeldari knowledge is stored and protected by the Harlequins
• The masques of the Harlequins: structure and organization of a masque which is at once an army and a troupe of players. These are the collectives in which the Harlequins wage war, and here they are presented with examples, runes, and troupe markings
• Descriptions of 10 Masques and their respective runes - The Midnight Sorrow, The Veiled Path, The Frozen Stars, The Dreaming Shadow, The Growing Scorn, The Silent Veil, The Endless Dance, The Twisted Path, The Shattered Phantasm and The Reaper's Serenity
• The Dance of the Ages: A timeline chronicling major events and battles in Harlequin history from the fall to the present
• Background information on all units available to Harlequin armies
• A gallery full of beautifully painted Citadel miniatures, with example armies and photos ranging from stand-alone models to images of models in battle scenes on designed terrain.

Rules

Everything you need to deploy your Harlequin army in games of Warhammer 40,000 is here:

• 9 datasheets with rules for using each Harlequin unit in your games of Warhammer 40,000 - including the Webway Gate, an Aeldari terrain feature
• Weapons of the Masques: Profiles for all of the Harlequins' melee and ranged weapons and gear
• Point cost for all miniatures, weapons, and gear for use in matched play
• Labyrinth Travelers: Rules for battle-forged armies, including:
• 6 Masque Styles: Bonus abilities specific to the following masques - The Midnight Sorrow, The Veiled Path, The Frozen Stars, The Growing Scorn, The Dreaming Shadow, and The Silent Veil
• 25 unique Stratagems, 5 of which are reserved for the following Masquas - The Frozen Stars, The Dreaming Shadow, The Growing Scorn, The Midnight Sorrow and The Silent Veil
• Mysteries of the Black Library: 13 weapons and artifacts only usable by the Harlequins
• Discipline of Phantasmancy: 6 psychic powers unique to Harlequins with the psyker keyword
• 6 unique Warlord Traits for the Harlequins, plus an additional 6 for the following masques: The Frozen Stars, The Dreaming Shadow, The Growing Scorn, The Midnight Sorrow, The Veiled Path, and The Silent Veil
• 6 tactical objectives unique to the Harlequins.