This badge was awarded between May 19 (07:00 UTC) and June 1 (06:59 UTC) to people who subscribed 1 regular/gifted/anonymous subscription to any channel streaming in the LEGO Batman: Legacy of the Dark Knight category with drops enabled. Prime subscriptions did not count.
It was added for the launch of the game, which released on May 22 from TT Games and Warner Bros. Games, alongside a Twitch Drops campaign that rewarded in-game Batcave props for watch time.