Pre Order activation key will be available at the planned release date:
29 Mar 201603:00
The Season Pass consists of over 40 new characters and 5 exciting new levels based on content ...
The Season Pass consists of over 40 new characters and 5 exciting new levels based on content focused around Marvel’s Agents of S.H.I.E.L.D. and Classic comic versions of Black Panther, Doctor Strange, Captain Marvel and Masters of Evil. As an added bonus, Season Pass holders will also have exclusive access to The Avengers Explorer Character Pack
In order to activate this game, you will require a third-party 'Steam' account. For full details on how to activate please follow this link: https://support.steampowered.com/kb_article.php?ref=5414-TFBN-1352