Blizzard bringing a new playable character to Diablo 2: Resurrected - the first new character the game has had in 25 years - could be the start of an era of active development for the classic game, potentially seeing it evolve like a modern game does.

To recap quickly: Blizzard shadow-dropped the warlock for Diablo 2 last night as part of a paid expansion release and a wider 30th anniversary celebration for the Diablo franchise. Not only was this unexpected but it's a 'testing the waters' moment; should the warlock go down well, Blizzard will take it as a green light to explore more of this kind of thing going forward.

"We are excited for the opportunity we have right now to see what the community says about what we're making," said Timothy Vasconcellos, lead designer on the Diablo Legacy team, during a Diablo 2 interview at Blizzard headquarters a couple of weeks ago, which I was a part of. "And if we're trusted with that legacy and if it's a positive reception and they say: no you guys actually did do this very intricate dance preserving the 1999 game, then maybe we can think about how we pursue those opportunities in the future. But we have to nail that otherwise we kill the game in trying to progress it forward."

"We still have millions of people who play Diablo 2 - millions of them," lead producer Matthew Cederquist added, with a heavy emphasis on the "millions". "We saw the 30th anniversary of the franchise itself as a really great opportunity to surprise and delight. I don't think anyone expects a new class and all these features in Diablo 2, and I think that's going to be a moment that's like, 'I'm sorry, what did you say? You did what?' People won't believe it until we put it in their faces. And I sure hope it's as epic to the players as we find it. But is it a declaration of something new [going forwards]? We're going to have to see what the players say."

"We don't want to mess up the Mona Lisa. We're not going to give her some sunglasses and a new hairdo"

Understandably, bringing a new class to a treasured game like Diablo 2 was a nervy moment for the team. To my eyes, which aren't particularly accustomed to Diablo 2, the warlock feels at home in the game (I had a chance to play it for half-an-hour or so). Blizzard said a lot of effort went into making the class feel like it was designed in the year 1999, which I think it does. The team at Blizzard, more than anyone, perhaps, is aware of what's at stake if it messes around with the recipe too much.

"We don't want to mess up the Mona Lisa," Cederquist said. "We're not going to give her some sunglasses and a new hairdo. But at the same time, does it feel weird [adding a new class]? No. Do we have to honour that legacy of what was created? Yes."

Incidentally, the versions of the warlock differ in the Diablo games it's coming to - Diablo 4, Diablo 2, and Diablo Immortal. Broadly, there's a lore-based thread running through them, with all three telling a connected story of the warlock appearing in the world of Sanctuary. This starts in D2 and runs through Diablo Immortal and then Diablo 4. Diablo 2's warlock take also pulls on the game's more hardcore appeal, especially in the demon taming skill tree, which is unique to D2, whereby you can tame demons and have them fight with you as pets or consume them for bursts of power. It's fiddly but incredibly satisfying to do.

Should the community like the warlock, then, and want more, it will lead to a broader exploration of what Blizzard can do with Diablo 2. This might involve meaningful reworks of classes already in the game, for example, although were this to be the case, Blizzard wouldn't spring it on you like it did the warlock. "Let's say if we wanted to change Barbarian for some reason: I wouldn't want to surprise people with that," Cederquist said. "That is working with the community hand in hand, to listen to their feedback about the changes that we would make if we wanted to."

There's a bigger concern with this, though, and it's what happens to the preserved and restored Diablo 2 experience that millions of people clearly still enjoy? It's not a classic experience any more if it's changed. To this end, we've reached a divergence point. There are now, effectively, two versions of Diablo 2: Resurrected. There's a progressive version represented by Reign of the Warlock, which is the paid expansion the warlock is a part of, and there's the classic version known as Diablo 2: Resurrected.

"It's the reason why we separated out Reign of the Warlock and whatever future stuff we have, so that we do have the opportunity to change with feedback, but also preserve what people love in Resurrected, and all that data set is totally split," Cederquist explained. "Resurrected is going to time-stamp. If you don't want to play a warlock for whatever reason and you hate loot filters, you can still have Resurrected and it's going to stay there. If we make any future changes to any classes or whatever, it's going to happen in that Reign of Warlock space."

It's a big week for Diablo 2, not only with the addition of a new class, but also because it was released on Steam yesterday and on Game Pass (the Reign of the Warlock expansion is not included on Game Pass). There are already "millions" of people playing the game, as Cederquist said, and these releases potentially widen the game to millions more.