Rather than simply write a review of #31120 Medieval Castle, I wanted to take a fresh approach with this three-year-old, 3-in-1 set. As I opened the bags and saw the three sets of instructions, the answer became clear… LEGO sets are meant to be deconstructed and rebuilt, tapping into your creativity to make something new.

#31120 Medieval Castle – a popular Creator 3-in-1 set for MOC builders.

Creator 3-in-1 sets emphasize this by allowing you to build multiple models from one set of bricks, showcasing both the designers’ and builders’ inventiveness. But why stop there? I decided to use this as a learning exercise to show people how to get started creating a MOC (My Own Creation) with a limited selection of parts. To give me more parts to work with, I purchased a second copy of the set and challenged myself to design a custom medieval castle using only the pieces included — and in a single weekend! As you will see, I’ve tried to stay true to the set’s theme while exploring the process of building something unique.

I’ll also dive into LEGO’s original vision for the Medieval Castle and discuss how to expand upon it. Along the way, we will explore online resources that can inspire you to bring new life to your existing bricks, and I’ll showcase impressive builds that others have crafted using this set. By sharing both my own experience and the creativity of the wider LEGO community, I hope to inspire you to push the boundaries of your own building projects.

Creator 3-in-1 – Medieval Castle

About the set

#31120 Medieval Castle is a set released as part of the Creator 3-in-1 line of sets. Released on the 1st of August 2021 and retiring later this year on the 31st of December 2024, this set saw a long 3 year life, longer than many modern LEGO sets. Being a non licensed set this set is very fairly priced coming in at $99.99 (£89.99/€99.99) for a staggering 1426 pieces. This giving it a great price per piece of 7.0c (6.3p/7.0c). The main build, the castle, utilizes space super well, sizing in at 10.5 in. (26 cm) high, 12 in. (31 cm) wide and 11 in. (28 cm) deep, making it a great size both for play and display.

Three builds in one set

The LEGO Creator 3-in-1 line is a series of sets designed to offer multiple building experiences within a single box. Each set includes instructions for three different models, allowing builders to create, dismantle, and rebuild using the same set of bricks. The aim of the 3-in-1 series is to encourage creativity, flexibility, and extended play by giving builders the tools to explore various designs without needing additional sets. While the line covers a wide range of themes, from vehicles and animals to buildings and fantasy worlds, #31120 Medieval Castle focuses on exploring different aspects of medieval life, all using the same set of pieces to give builders multiple building options and indulge in hours of imaginative building.

The primary model, and what is seen on the front of the box, is the Medieval Castle. This build is a detailed, modular castle with a functioning drawbridge and portcullis. The build features a courtyard, two towers, and multiple rooms, including an armory and a blacksmith’s workshop. While minifigures are common to all the builds, the main build includes a brick built dragon, adding depth to imaginative play.

The castle is the main build, utilizing all of the included pieces.

The first alternate build is a tall, fortified tower designed to serve as a defensive outpost or watchtower. It includes a drawbridge and a small marketplace area. Though smaller than the full castle, it captures the essence of medieval architecture with defensive elements and features a working catapult to complement the setting. (Image: The LEGO Group).

The tower alternate build comes with a catapult play feature.

The second alternate build is a medieval marketplace, complete with a stone bridge, a windmill, and a small prison tower. This model highlights the civilian side of medieval life, offering a space for trading and commerce, while still providing defensive elements like the tower. Of the three builds this is the smallest, utilizing the fewest pieces. (Image: The LEGO Group).

This simple market is small and basic, the smallest of the three builds. (Image: The LEGO Group).

My experience custom building

Getting started with building a custom set is always daunting, but the hardest step is getting started. I have built many custom LEGO sets in the past but rarely do I build custom models under tight restrictions. While having close to unlimited options with pieces, and the wealth of the sources to pick up any elements you are missing, sometimes building with limitations forces you to be extra creative. I have particiapated in various master builds at LEGO conventions but I would not call myself an expert in building with restrictions by any means. I only share this to encourage others to not feel daunted by the pressures of building and should you wish to get involved in custom MOC building, picking up and repurposing a set you already have is a great way to get started.

With each of the two copies of the #31120 Medieval Castle containing 1,426 pieces each, I had nearly 3,000 pieces to work with—a sizable number. My first reaction upon opening the bags was “there is a lot of 194Medium Stone GreyLight Bluish Gray in this set”. The first step was to get a sense of what was included in the set and sort the pieces. While it might be tempting to jump straight into building and storyboarding, the limited number of pieces meant I wanted to avoid getting overambitious and running out of the parts I needed, which would leave me stuck. To better understand what I was working with, I began by knolling. Knolling is the process of arranging related objects in parallel as a method of organization. This approach is commonly used when parting out LEGO sets, as it allows you to easily see the contents. Many builders knoll sets before building as an enjoyable and relaxing extension of the LEGO hobby. Author Thita at TheBrickBlogger has a great article on the Art of Organizing through Knolling, which I highly recommend for those interested in learning more.

Once I had a good understanding of the available pieces and the scale I could work with, it was time to start building. I chose to continue the Castle theme from the original set and identified some key details I wanted to preserve in my custom model. Before diving into the build, I quickly sketched out a plan. Having a clear vision of what I aimed to create helped me stay focused as I developed my design. I wanted to ensure that all the following elements were incorporated into my build—features that, by the end, I felt I successfully achieved.

• Part of the model must be on water and there is a river running through the castle
• The city must contain at least one tower and have battlements around the exterior wall
• There must be enough space inside the castle to contain details
• The focal point of the castle must be the inclusion of an inn, this inn will have a sloped roof

While there was a lot happening in my model, I wanted to make sure the space felt inviting. To achieve this, I focused on ensuring the entryway was rich in detail. I built a small watchtower perched atop the castle walls, with a coat of arms displayed above the entryway, using the extra weapon and armor pieces I had. Instead of keeping everything at ground level, I decided to raise the interior of the castle by one brick, adding height and variety to the build. From the front, the contrast in colors and shapes captured the essence of what I envisioned. Though not perfect, it met the goals I set—to have fun and learn along the way.

I used common themes from the original set as influence for the model.

With my plan in place and several design sketches ready, it was time to begin. The foundation was the first thing I built. For my model, I decided that half of the structure would sit over water, allowing me to get creative with details like the inclusion of a watermill (from the original set) and a small bridge. While working on the foundation, I realized that the original set has a very square shape, and I wanted to introduce some curvature to the exterior wall. It’s unrealistic to expect all structures to be perfectly square, especially considering landscape limitations, so I used hinge pieces and layered tiles to angle the two halves of the wall by approximately 15 degrees. Although this is a small angle, it makes a noticeable difference and enhances the build. Even though I’m creating a custom model, it’s worth mentioning that the original set had some excellent design decisions that influenced my build. See if you can spot which parts of my model were inspired by the original set!

Even slight curves can add variety.

I was surprised by the variety of pieces available in this set. Just by looking at the box, it’s difficult to get a full sense of what’s included, but as you build and explore the parts, the creative possibilities really start to flow. One of my core goals was to include an inn, making it the centerpiece of my model. Built over the water, I used slopes to create a rocky texture on the side of the structure. By combining curved and square bricks of different sizes, I aimed to give it a weathered look. The SNOT (Studs Not On Top) technique helped me embed some roots and leaves into the side, adding a more organic feel. Having recently built the #10316 Rivendell set, its design was still fresh in my mind and influenced the upstairs interior of the inn. Inside, I created a bed, nightstand, writing table, and chair. With the abundance of 24Bright YellowYellow pieces included in this set, I decided to use them for the exterior of the upper-level walls. Since I wanted to use as many pieces as possible, this felt like the best spot for them. When contrasted with the warmer tones of 192Reddish Brown wooden beams on the roof, the brightness of the yellow wasn’t overpowering. Instead, it contributed to a cozy, balanced scene.

Interior details add to the beauty of LEGO building.

The original set had many impressive features, and it was important for me to preserve those details in my model. The watchtowers were the most significant elements I aimed to replicate, drawing a lot of inspiration from the original design. Everything from arrow loops to the battlements was well captured. The merlons and crenels of the battlements utilized inverted slopes, which not only created a more spacious appearance but also added an extra layer of detail through depth. One of the key aspects that can enhance a build is moving away from flat surfaces. While it’s easy to stack a large number of similarly colored flat bricks, introducing even slight variations can add considerable detail. In the image below, I demonstrate how using just six different types of bricks can create great wall texture, whether through masonry, curves, slopes, or slight indentations achieved with panels. If the walls had been flat, I wouldn’t have been able to capture the old, weathered look I was aiming for. Similarly, the use of SNOT (Studs Not On Top) techniques on the lower inn wall allowed me to incorporate foliage detailing, adding even more variety.

Wall texturing changes what otherwise would be a flat wall into a detailed wall.

Although the exterior is what most will notice, I wanted to truly capture the bustling interior of the castle. While size limitations due to the number of pieces were a factor, I felt I used the space efficiently, incorporating a wealth of details. I believe it’s important for a model to be presentable from all angles. This approach not only encourages thoughtful design decisions and prevents cutting corners but also allows for the inclusion of numerous intricate details. While many of these elements may be difficult to see at first glance and might only be noticed upon closer inspection, they contribute to the overall experience of the build. Understandably, some concessions may need to be made due to piece restrictions, and if it means sacrificing hidden details to enhance the more visible aspects, that’s a reasonable decision.

The city is bustling with life.

While it can be tricky to see due to the narrow roads—an unintentional design choice that arose from running out of parts—I was able to fit a lot into the small space. Among the details I included are a target practice tree, a winch for hoisting objects out of a boat, a water wheel (featuring a Technic build that turns as the water wheel spins), a jail cell, an armory, a bridge, a well, a signpost, and even a market stand. The interior details were the last elements I added, and while it was enjoyable to fill the space, this led to some challenges due to the congested nature of my build. There were times I had to disassemble parts of my walls to incorporate details underneath. By the time I finished adding all the elements I wanted, I was down to my last 200 pieces. Although I aimed to use as many pieces as possible, I ultimately decided not to overwhelm the build and made a conscious choice to stop adding just for the sake of it.

A lot of items fit in a small space.

In this section, I shared my experience building and some of the details I included in my model, but I want to emphasize that I am far from an expert MOC builder. This example demonstrates how, with slight variations and by using only the pieces from an existing set, you can tap into your creative potential and build something new and unique. Now that I’ve established my foundational set with the available pieces, I plan to expand on it using all the other parts in my collection to enhance the model further and address some of the compromises I had to make due to limitations.

One thing that stood out to me upon finishing the build was the model’s stability. While creativity is essential for building, it alone does not make a good LEGO model builder. Many decisions I made in my model would not pass muster in an official set, and the lack of stability in this build was concerning. I nearly broke it several times during construction. Nonetheless, it was all a fun learning experience. I hope that by sharing this, I encourage you, the reader, to embark on a similar journey, perhaps rebuilding some of the sets you have sitting in storage or collecting dust on a shelf. Practice makes perfect, and the exercise of rebuilding can work wonders for both your creative mindset and your enjoyment of LEGO.

Mastering the parts palette

The LEGO Group produces thousands of unique parts, each with a variety of connection types. To help builders navigate this expansive palette, Tom Alphin has created a comprehensive Parts Guide, which provides a detailed overview of the most common LEGO elements. This guide not only highlights frequently used parts but also organizes them into categories based on function and connection types. Utilizing resources like this can significantly enhance your building skills, allowing you to better visualize how pieces connect and plan your creations more effectively. Personally, while writing articles and building custom models, I’ve frequently referenced this guide and continue to discover new insights with each use.

By understanding the parts available you have a better grasp of what you can build.

Rebrickable

As the article explores how to give new life to LEGO by rebuilding with the parts available it would be a great loss to not mention Rebrickable.

Rebrickable is a great way to get ideas to breath new life into existing sets, either through free or paid instructions that people share.

I am not the first, nor will I be the last person to disassemble #31120 Medieval Castle and build a custom castle. When you look at the plethora of creations talented MOC builders have created you can see how even with limited parts you can build some great models. As part of my investigation I decided to highlight three models that I felt stood out the most and were noteworthy to deserve a callout. It is important to note that the builds I have referenced here are picked solely from an observation point of view. Given that some of these builds are not free instructions I have not purchased the builds and cannot comment on the instructions or build experience. The goal of highlighting these builds is to both showcase some of the great models people have built, and to serve as a inspirational piece to help you, the reader, see all the great modifications of existing sets that can be found on Rebrickable.

The first build that caught my attention was designed by builder BrickType and involves picking up two copies of #31120 Medieval Castle and building a larger castle. A lot of the core set themes are employed here with the Gatehouse, the Blacksmith and the Tower each making a comeback. Of the three builds this has the least deviation from the original set and feels like an expansion of the original set. In my opinion the most impressive modification is built by designer Made With Brix. This designer has built a variety of builds using various copies of #31120 Medieval Castle, with my favorite being the Black Falcon Knights Castle. This MOC is built using 3 copies of the original set and feels robust, detailed and is packed with intricacies. Looking at the image alone it baffles me that such an amazing build can be made with parts in this set alone. This designer has also created larger builds using the original set, with one using four copies!. The final builder that caught my attention is a reimagination of the Dungeons and Dragons: Red Dragons’ Tale released this year. This free set of instructions by designer MIJbricks captures the details of the set it is trying to replicate beautifully. While smaller than the original Dungeons and Dragons: Red Dragons’ Tale set, it is a great way to get a rendition of this set for a fraction of the price. Given it is a free set of instructions, I highly encourage anyone who picks up #31120 Medieval Castle to try to build a custom model take a stab at MIJbricks’ creation.

Many great designs can be found on Rebrickable.

Bricklink

You have your ideas and your sets—now it’s time to build. Securing the necessary bricks can be challenging, especially if you’re unsure where to start. LEGO pieces can be sourced in a variety of ways, whether through purchasing complete sets or individual bricks, with both official and third-party options available. If you’re using Rebrickable to create an alternate build of an existing set, buying additional copies of the set is often the most cost-effective way to gather parts. However, purchasing individual pieces can quickly become expensive. LEGO’s Pick a Brick program allows you to buy specific parts directly, but these can sometimes be pricey. A more affordable alternative is Bricklink, a popular site for buying individual pieces. If you’re unsure of a part’s name or ID, using a resource like BrickArchitect’s Parts Guide can help you quickly locate the piece you need.

Bricklink is a LEGO builder’s dream. A great way to purchase parts for custom builds.

Closing thoughts

Stepping away from building what LEGO intends you to create is not only fun but also allows you to tap into your creative mind and generate new ideas. Building custom builds is a fantastic way to learn construction techniques, gain experience with the wide array of pieces in LEGO’s arsenal, and enjoy the process. However, dismantling what you’ve built and crafting custom models using only the available pieces adds an extra layer of fun.

Many people want to start custom building but feel daunted by the process. As with everything in life, practice makes perfect, and working within limitations encourages creativity. Even if custom models aren’t something you’re particularly interested in, I encourage everyone to try breaking down a set with a large number of repetitive parts and build something new with them. If you’re reluctant to dismantle your existing models or don’t have spare pieces, consider picking up one of the many excellent Creator 3-in-1 sets, such as the #31120 Medieval Castle, to get started.