Designer Diary: Sylvion and Castellion, or Oneiric Onslaughts in the Oniverse

Sylvion was born out of my desire to create a "tower defense" game in the Oniverse.

I always had a thing for this type of game, maybe because they have so much in common with board games. I thought I could rip a few pages from their book such as resource management, positioning strategies, and coordinating timing.

For my grandmother reading this article, a "tower defense" game is a game in which you need to defend a place, often a castle or a fortress, from evil foes charging in waves. You then have to place towers, barricades or heroes in their way to try to stop them before it's too late. In recent years, Fieldrunners, Plants vs. Zombies, and Kingdom Rush are among the most successful games of the genre.

The theme came to me while remembering the beautiful German forest – I was in Germany for The Marriage of Figaro – and instead of defending a fortress, I wanted the players to protect the Forest of the Oniverse. Fire and flames were the natural enemies, facing an alliance of animals, fountains and floral creatures, each one bringing a specific power.

The draft aspect was the other key element that I wanted to integrate in this game. Instead of playing with the same group of defenders every time, players now have to draft a few of them before each confrontation, giving the players the opportunity to build their own deck for more personalized strategies.

Once a deck is completed, the goal is now to survive the Ravage and its many waves of attacks. Its army and maneuvers are represented with cards, which are divided in four decks. Each of these decks is assigned to a specific zone of the forest.

A game round starts with the revelation of the top card of every Ravage deck and the movement of all of its minions. If one of them reaches the forest, it inflicts a certain amount of damage to the forest — and if the vitality of the forest falls below zero, the game is over.

To prevent this from happening, it is necessary to manage your cards correctly, placing fountains in strategic places and playing the right animals at the right time. But all of these cards have a cost, and you'll need to discard other pieces of your hand to play each of them.

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The starting point of Castellion was entirely different: to create a game without any hand to manage.

Even though Onirim, Urbion and Sylvion have very different mechanisms, their objectives and development share a lot of similarities, with the three of them requiring players to manage their cards as well as timing. In these conditions, knowing when to play or discard a card is as important as which card you're actually playing or discarding.

With Castellion, I wanted the decisions to be instantaneous: At the beginning of a turn, the player draws a card and needs to decide immediately if they intend to play or discard it. And since they have no hand of cards, the management takes place somewhere else: the spatial organization of the played cards. Players then need to build something only with these cards: a structure, a building, or perhaps a castle!

After only a few test runs, I decided to replace the cards with tiles as they were much more stable and gave a better sense of construction.

Speaking of tiles, I thought it would be interesting to add a special power to the discard action so that it would create a greater dilemma. This power would then serve to make the castle stronger, able to defend itself.

But to defend the castle from what? That's right: I needed a new villain!

That's when I had the idea of a shape-shifting monster inspired by The Thing by John Carpenter, this cinematic trauma visited on my nine-year-old self. To defeat this entity, the castle has to imitate the monster and also change its form, always getting bigger and stronger so that it might resist the monster's three assaults, each of them more brutal than the last one.

These attacks are triggered when enough Traitor tiles, which are shuffled among the other tiles, are picked and placed. This system creates a great deal of pressure, forcing the players to choose between short-term and long-term preparation, for you never know when the first assault will occur!

The castle's tiles are called Defender tiles, and they represent both a piece of your castle and a defender. There are four types of defenders, each of them carrying a unique shape and a specific power. This power is activated whenever the tile is discarded, whereas the color indicates how and where to position this tile following a defensive formation.

You will need to master these different defensive formations in order to defeat the Menace, and using the right one depends on what form the Menace adopts to attack your castle. For example, if the Menace takes traits of a harpy, your castle will need high towers to defend itself (with these towers being made by aligning columns with tiles of the same color); if the Menace comes at you in a horde instead, you'll need to put up lines of defense (i.e., rows with tiles of the same color).

In the end, Castellion presents itself as a descendant of my childhood puzzles, a puzzle we can do over and over again because of its changing form and versatile pieces. It invites the player to explore all possibilities, but at the same time, reminds them that this is a race against an unavoidable menace.