The Guild Wars Nightfall Prerelease Bonus Pack is a new retail package for the upcoming new campaign Guild Wars Nightfall.
From the official Press Release:
- The Guild Wars Nightfall Prerelease Bonus Pack is expected to hit store shelves on September 15 and will feature:
- Guild Wars "Play Now" key for a 10-hour/14-day trial* of Guild Wars Prophecies and Guild Wars Factions
- Guild Wars Nightfall Bonus Key, providing one additional character slot for a Guild Wars Nightfall account, as well as two exclusive items for the new professions — a Fiery Sunspear of Shelter for the Paragon and an Icy Soulbreaker of Enchanting for the Dervish
- Mini strategy guide, concept art, screenshots, in-game renders of characters and items, preview trailer, wallpapers, lore, quick reference card, music, and more!
- * The trial code is for a maximum of 10 hours of game play over a 14 day period from the time the key is activated.
Note that - as stated on the box - the full version of the game is not included!
Also, unlike Factions preorder this package does not grant earlier access to the game.
To prevent misunderstanding it's been confirmed again by ArenaNet and NCsoft that the character slot that comes with the Prerelease Bonus Pack really is an addition to the ones that come with the game, giving you 3 slots for a merged account or 5 slots for a stand-alone Nightfall account. 
The Prerelease Bonus Pack adds the Fiery Sunspear of Shelter and the Icy Soulbreaker of Enchanting to all characters that are in a Nightfall account, or even a merged account.
The weapon stats are as follows:
- Fire Damage: 14-27 (Requires 9 Spear Mastery)
- +7 Armor vs. Physical Damage
- Energy +5
- Cold Damage: 9-41 (Requires 9 Scythe Mastery)
- +15% damage while enchanted
- Enchantments last 20% longer
To gain these items, type /bonus while in a town or outpost. They will appear in your inventory, and will be customized for the character who gained them. This can be done as many times as you wish, on as many characters as you wish, unless the character currently has the items in his or her inventory.