The provided article text consists entirely of PC Gamer's website navigation, membership promotions and menu boilerplate, with no actual article content about Marvel Tōkon: Fighting Souls beta dates or playable content included. As a result, there is no substantive information available to summarise regarding the beta's start time, duration or which characters and modes will be accessible.

To provide an accurate summary, the full article text would need to be retrieved, as the current content only contains site-wide headers, sign-up prompts and category links rather than the actual reporting on the game.