Blizzard's take on the lane-pusher genre had maps of various shapes and sizes, but it was missing a one-laner until now. With their latest, the Lost Cavern, Heroes of the Storm [official site] wants to give the community something they were apparently already trying to make on their own: a map with no objectives, no lane pushing, and just one unending teamfight in the middle.
Predictably, it won't be part of the competitive side of the game. More surprisingly, it won't have its own dedicated queue: people will have to personally invite their friends to enjoy it. And it won't be quite an ARAM map. Just an AM, without the random.
ARAM stands for All Random All Mid and it's a consolidated practice in the MOBA genre: all players are assigned a random champion and they cannot heal back up at their base. All they can do is head down the middle lane and fight to their death. It's a great way to play some low-pressure games without having to think about strategy or objectives, and maybe learn the basics of a new hero in the process.
Of course, it's never very balanced: some heroes just aren't made for it whereas others become oppressively strong, and some skills are rendered useless without a map to play with. But it doesn't really matter: the randomness ensures the overpowered champions cannot be exploited systematically, and while it's never entered the competitive realm, it has remained very popular as a fun mode to wind down - or warm up - without the stakes of a real game.
Heroes of the Storm didn't have a one-lane map or an ARAM option before, but a meaningful number of players were using the existing maps to play ARAM anyway. Blizzard decided to make their life easier by giving them Lost Cavern, a proper one-lane map designed with this sole use in mind.
However, Lost Cavern will only be available in custom games, with no dedicated queue and matchmaking, meaning that players will not be automatically paired with strangers of their own skill level: they will have to manually invite other players to join their own game, or fill the ranks with bots. Also, unlike ARAM, hero selection will not be random, which could make some heroes oppressive and discourage the use of others.
Still, choosing to cater to a niche in their community is very nice of them, even with all these limitations in mind, and there's no reason why they couldn't follow up on it and make some adjustments in the future. The map should become available with the next patch.