Sometimes, when an indie developer finds success with a game, they double down on the property instead of moving on to new projects. This is always a bittersweet thing: since the studio has demonstrated greatness, you want it to try different things; but because the game is amazing, you want it to stick around for as long as possible. For the past three and a half years, developer Massive Monster has done something similar: rather than release a new IP, it has reinvested in its 2022 hit Cult of the Lamb, an exceptional amalgam of colony building and Rogue-like dungeon-crawling. Since launch, the studio has distributed multiple free updates that have expanded the narrative and mechanical boundaries of the base game. And just last month, it dropped its biggest and boldest piece of post-launch content yet: Woolhaven, a paid expansion pack that adds new story content, dungeons, weather effects, and mechanics.

Woolhaven is woven into the fabric of the base game. If you've already defeated the Bishops from the vanilla version of Cult of the Lamb, a statue will appear on the north side of your base. Once you dedicate a certain number of resources to the statue, you will resurrect what is left of Yngya, the mother goddess of all lambs, and open the path to Woolhaven, the birthplace of your clan. At the behest of Yngya's spirit, you will then explore the surrounding lands, shepherding lost souls back to the "Cold Mother" and ridding each area of heathens and interlopers.

Woolhaven is a fascinating piece of world-building. The story of Yngya and her flock is entirely new, and yet it fits seamlessly into the sinful, chaotic, ruthless reality of Cult of the Lamb. Despite its freshness, it feels like it's always been there, waiting to be discovered. It adds weight and texture to the already sinister narrative from 2022, and infuses the proceedings with a healthy amount of pathos. The titular Lamb is the last of its kind, its ancestors hunted and slain long ago, its ancestral home covered in rot, its ancient goddess a grim shadow of herself.

A new storyline is only the beginning in Woolhaven. It adds so much more, and in the process seriously elevates the overall package. For starters, it introduces two new full-length dungeons, with unique monsters, bosses, NPCs, and curses. There's also a brand new weapon type, the flail, which is excellent. The three-hit combo lashes out with one spiked ball, then the other, then both at once. And the heavy attack will actually pull you toward the targeted enemy. 

The most interesting novelties, though, involve your cult. That shouldn't come as a surprise to those who logged dozens of hours in the main campaign. The simulation aspect of Cult of the Lamb always outpaced the combat phase, and that relationship endures in this expansion. Combat has gotten better, for sure — thanks in part to the heavy attack option added previously in the "Relics of the Old Faith" update — but it still lags behind cult management, which is absolutely brilliant this time around.

The most essential new features revolve around a game-changing winter survival system. By awakening Yngya, you have also brought winter back to the land. At first, your followers are intrigued. They play in the frost and catch snowflakes on their tongues. Soon, however, the terrible truth of the situation reveals itself. In the winter, soil freezes over and refuses to yield crops; and followers, unless they are sufficiently warmed, freeze to death. If you previously defeated the Bishops and unlocked the way to Woolhaven, it's safe to say your cult was a well-oiled machine. Well, winter is the wrench in that machine.

It makes everything that much more desperate and grave, which is honestly great. Cult of the Lamb works best when the threat of failure and death is all around you, and you must use quick-thinking, careful planning, and strategic sacrifice to keep your followers happy, healthy, and faithful. And the winter system is geared to create just that feeling of urgency, to never allow you to feel fully prepared. Indeed, as you return souls to Yngya, the effects of winter will grow more intense. Phase one brings snow; phase two, blizzards; and so on. But worry not: the game provides new tools to survive each cold snap. These include the Rotburn furnace, a sauna to warm up freezing cultists, and a ranch to raise livestock.

The ranch is one of the highlights of Woolhaven. By discovering the lost soul of Baraq, one of Yngya's most devoted disciples, you can unlock the tools needed to construct your ranch, and populate it with animals like alpacas, yaks, and even turtles. The ranch is there, ostensibly, to feed your cultists during the winter when crops refuse to grow, but you can also gain valuable resources from living animals, including milk and wool, the latter of which is the primary form of currency used by the ghostly denizens of Woolhaven. You can also pet, feed, and even walk your animal companions. It makes the cult feel more alive and dynamic.

The final piece to the puzzles is rot. The mountain beyond Woolhaven is sick with it. Yet, it's not all bad. At certain junctures on your dungeon dives, you'll run into a strange material that "seems as stone, yet feels like flesh, growing from the ground like something tumorous." By breaking this material apart, you'll earn Rotburn, which powers your furnace during the dead of winter. And, if you unlock the right blueprints, you can establish Rotburn mines within your cult, giving yourself a little cushion for those lean periods. But that's not all. You can recruit rot minions, a special kind of cultist who will work continuously day and night without the need for sleep or food, although they die after only 10 days. This adds yet another strategic wrinkle to the mix.

Because of all these additions, Woolhaven is a fairly substantial expansion pack. It should take you about 15 hours to finish the campaign, compared to 20 for the base game. As a result, the $16.99 asking price seems appropriate. 

Also appropriate: the audiovisual aspect in Woolhaven, which retains the cute-gross vibe of the original. The new creatures, NPCs, and follower forms are alternately adorable and monstrous, and there's a feeling of infestation and disease throughout each dungeon. And the music is as splendid as ever. Composed primarily by Narayana Johnson, aka River Boy, who sadly passed away last year, it's once again pitch perfect: ambient and atmospheric at times, dripping with decay at others, boldly mixing unlikely genres at yet others. The Executioner boss track, for example, is quite unlike anything you've heard in a similar game.

While the visual landscape of the expansion remains great, it suffers from a few strange visual glitches and artifacts — just like the original game, at least on Switch. 

Woolhaven is proof that Massive Monster made the right decision to stick with Cult of the Lamb. By retaining everything the vanilla version does right, and adding several novelties — a somber story about the Lamb's lost clan, two new dungeons filled with unexpected horrors, a wintry weather system that changes the rules of survival, and consequential ranching and rot mechanics — the expansion takes what was already a great game and makes it even better. If you own and love Cult of the Lamb, make sure you pick up this expansion as soon as time and money allow. And if you've never heard of the game before now, consider this the optimal time to invest.