Diablo 4 ends with a bit of a cliffhanger. Though Lilith is defeated and Sanctuary saved for a time, another threat, Mephisto, still looms. Seeking to put an end to the Lord of Hatred once and for all, Neyrelle traps Mephisto’s essence within a Soulstone before disappearing, leaving only a cryptic note as to her intentions. Enter Vessel of Hatred, Blizzard’s first expansion for Diablo 4 releasing on October 8, where players will race to find and help Neyrelle in her struggle before it’s too late.

Ahead of the release of Vessel of Hatred and alongside the debut of a new in-game cinematic highlighting the physical and mental toll Mephisto’s presence has taken on Neyrelle, we got the chance to chat with game director Brent Gibson and associate narrative designer Eleni Rivera-Colon about Vessel of Hatred’s cast of characters. How is Mephisto’s influence affecting Neyrelle? What is Mephisto’s goal, and what is he able to do while trapped within the Soulstone? What is Lorath up to? Gibson and Rivera-Colon wouldn’t spoil anything but did help set the table as to what players can expect to see as they journey through Vessel of Hatred’s story campaign.

In Vessel of Hatred, Neyrelle is seeking the Vault of Light, a location said to be hidden within the dense jungle of Nahantu and supposedly the final resting place of Akarat, the founder of the Zakarum faith. It’s there she hopes to be able to destroy Mephisto for good, but his presence within the Soulstone corrupts the world around her, catching the attention of the Spiritborn, the guardians of Nahantu’s jungles.

After teaming up with a new character, the wise Spiritborn elder Eru, players finally catch up to Neyrelle in the newly revealed cinematic. Soulstone in hand, she furiously recites ancient chants in an effort to control Mephisto’s power. Gibson said the scene is the moment the player character is “coming to terms” with the scale of Neyrelle’s situation and realizing that something must be done as she struggles to tame Mephisto.

“She’s doing everything she can with chants to hold him in the Soulstone,” Rivera-Colon said. “He’s essentially trying to break out. He’s going to do everything he can.”

Neyrelle believed that by accepting the burden of the Soulstone alone, she would be keeping her friends safe. Taking on heavy burdens and being forced to deal with situations out of her control is something that Neyrelle as a character is used to, Rivera-Colon said.

“In the expansion we get to really explore what she thinks about this choice and this decision now that she’s been with something like Mephisto and [the] Soulstone for so long,” Rivera-Colon said. “It’s going to take a heavy, heavy toll on her, and this is something she wasn’t sure if she was going to be able to do.”

As much as it’s a story about Neyrelle, it’s also one about Mephisto, too. Absent in Diablo 3, he played a supporting role in the story of Diablo 4, aiding players anonymously in his Bloodied Wolf form on their quest to stop Lilith before eventually revealing his true identity. Gibson said one of the goals of the expansion was to hone in on the Lord of Hatred and tell the next major chapter of his story, teasing that there is “still more to come” in regards to Mephisto that Blizzard will craft over time.

Mephisto is one of the Prime Evils, and though he is terrifying in his own way, he’s quite different compared to the demon from which the series derives its name, Diablo. Mephisto is more keen to sow hatred and division among the people of Sanctuary, finding vulnerabilities in people and turning friends and family against one another for his own nefarious purposes.

“That’s his MO,” Gibson said. “If you think about the way he shows up in the base game, making you second guess your allies, making you second guess Lilith. What kind of influence does he have on Neyrelle right now? What is he making her second guess?”

Though he is still trapped in the Soulstone, his wolf projection seen in the base game returns, once again serving as Mephisto’s voice and a way for him to “spread his message.” His corruption seeps from the Soulstone into the world around it, with Gibson describing the Soulstone itself as being almost radioactive in nature.

“It’s a pretty big deal that Mephisto is back on Sanctuary,” Gibson said. “Any time that happens, they get banished back to the abyss and have to kick and scream all the way back. Even though he’s stuck in the Soulstone, the danger here is if he gets out, he’s physically back on Sanctuary, and so it’s important Neyrelle finds a solution to not let that happen.”

Mephisto is trying to do everything in his power to break free, though his options are limited and so he must be careful, Rivera-Colon said. Thankfully for Mephisto, the expansion returns him to one of his old seats of power, the jungles of Nahantu where he previously corrupted the Zakarum church and battled players in Diablo 2. Gibson said that Vessel of Hatred is “revisiting history” in that way, but it’s clear that Vessel of Hatred is also expanding on the region and its lore, adding new wrinkles to the story of Akarat, the Zakarum, the Light, and the Spirit Realm.

“The Zakarum faith didn’t get everything right,” Rivera-Colon said. “They didn’t know Akarat. So it’s an opportunity to explore Akarat and Akarat’s faith not just through the Zakarum faith but through the land and the impact he had on the land throughout Nehantu.”

There’s no doubt the focus of Vessel of Hatred is on Mephisto and Neyrelle. However, one of Diablo 4’s main characters, the last Horadrim, Lorath, is notably absent. Gibson said that was by design, as they only had so much room for the stories they could tell in the expansion.

“Where Lorath is is a mystery,” Gibson said. “That will unpack over time, but if you think about the state of the world after the base game, he had some work to do.”

Blizzard is still leaving plenty of details for players to discover come launch day, though a recent trailer may have already spoiled one of the expansion’s boss fights. Thankfully, players won’t have to wait long to find out what happens next. Preloading for Vessel of Hatred is available now for PC players using Battle.net, while console players can preload the expansion October 5 ahead of its October 8 release. For more on Diablo 4, be sure to check out our hands-on preview with the new Spiritborn class, as well as read up on all the new systems, like Runewords, and the difficulty overhaul coming alongside Vessel of Hatred.