Happy New Year!  Not only does it mean 2016 is finally over (hooray!), it also means the Sub Terra Kickstarter is just around the corner!


If you’ve been paying attention to the ITB newsletter, you may have noticed that in addition to the Sub Terra base game, we’ll also be offering three modular mini-expansions themed around a militarised return to the cave following the events of the base game! Each adds a new character, some new tiles, and a bunch of new rules that together increase the depth of the core Sub Terra experience.  You can use any or all of them with the base game – they don’t need to be bought together or in any specific order.


The expansions are:

  • Sub Terra: Investigation
    Find your fallen friends and recover their powerful equipment to aid your escape.  Play as the ruthless Agent, who uses a custom selection of items to handle any situation.  Watch out for new “doom” hazard cards that make future hazards worse.
  • Sub Terra: Extraction
    A new type of fast-moving horror has made the cave a much more dangerous place.  Play as the cautious Mercenary, who can quickly scope out new tiles or entrench themselves against the swarm.  Carry proof of the infestation back to the surface, or die trying.
  • Sub Terra: Annihilation
    In a completely new way to play, re-enter the cave to deliver powerful explosives to sites of structural weakness, then escape before the detonation seals you inside.  Play as the brutal Exterminator, who can destroy horror tiles and is immune to the noxious underground gas.

If Sub Terra is inspired by the film The Descent, then these expansions are inspired by a mixture of The Descent Part 2 and Aliens.  Their focus leans a little bit more towards action-horror than the base game, but the survival elements are still as present (and as dangerous) as ever.

These expansions have been in active development since August, and they’re now in a very enjoyable place.  But why should you buy them?


Given board game expansions will always be played with the base game, I prefer to think of designing a set of “expanded games” rather than design each expansion in isolation.  For Sub Terra (ST) and its three expansions (ABC), this meant I was considering all eight of {ST, ST+A, ST+B, ST+C, ST+AB, ST+AC, ST+BC, ST+ABC} as individual complete games, and they were each tested accordingly.

Compared to designing a base game, I found designing an expanded game to be a bit different:

  • Players already know the core rules
    In terms of accessibility, the bar to entry is much lower.  Players only need to learn how the new rules work, and how they interact with the old rules.  The complexity budget for an expanded game can therefore be much larger for the same target audience, which allows for a deeper and more rewarding experience.

    However, the usual caveats about complexity / depth / lenticular design still apply.  Board (or state) complexity can increase exponentially with a linear increase in rules or component complexity.  This is going to be much less visible to you, the designer, who’s spent far too much of their life fiddling with this game system, so be careful not to overdo things and end up with an intractable mess.  Expanded games still need to be solvable.
  • Players already own the core components
    It doesn’t take many more physical components or rules changes to shake things up a lot.  You can either change the rules around how core components function (“core-Orcs now have twice as much health”), or your new components can influence how the core components work contextually (“new-Dwarves don’t take damage from core-Orcs”).  Collectible card game expansions are built upon this model – adding only a few new cards or rules can shift the metagame and drastically change how your decks and games play out.

    Fewer components keeps production costs down.  Well-designed expansion content can therefore be a cheaper way for players to acquire gameplay experiences of equivalent worth to a whole full new game.
  • Players know how to beat the base game
    Compelling game experiences are the ones that challenge you just the right amount – they’re neither so easy you get bored, nor so difficult that you get frustrated.

    At the point players are considering playing an expansion, they must have already got somewhat bored with the mostly solved puzzles of the base game.  It’s therefore not sufficient to simply leave exactly the same strategies in place and add content that’s purely superficial (this is obvious, right?).  The puzzles must change and the challenge level must increase to keep players engaged.

    However, it’s also not advisable to change the optimal strategies so much that they become completely unrecognisable.  Players have already invested a bunch of time learning strategies for the base game.  If the correct approach for the expanded game is something that needs drastically different skills, then they’ll (rightly) feel like they’ve wasted that time.  Ideally, optimal strategies for the expanded game should build on those from the base game, by stretching and bending them in different directions instead of throwing them away completely.
  • Players already like the base game
    This might seem like a positive thing, but it’s actually a serious constraint.  Not every player likes every game, but as long as enough people like your base game, then you’re OK.  However, the only people interested in an expanded version are people who liked the base game.  The more an expanded game shifts the experience away from that of the base game, the more of these players are going to dislike it, and the worse it will review/sell…even if the expanded game is a great game in its own right!

    This is another force against changing things too much, yet things can’t remain static else your players base will get bored (as argued above).  A sweet spot between the two extremes must exist, though finding it isn’t necessarily easy. 
  • You (the designer) already know how the base game works
    This is as critical as it is obvious.  There’s no way I could design multiple good new games from scratch in a matter of months.  You’ve already bent and broken the game system in countless ways throughout the core game’s iterative design process.  You know what ideas simply didn’t work, and probably have a good idea why they didn’t work.  You likely have a number of great mechanics that were cut due to complexity concerns, space concerns, or cost concerns.

    This makes designing and testing an expanded game much more efficient, as you’ve already done most of the work.

Sub Terra tries to hide its complexity behind incremental reveals and linked probability calculations.  The expansions continue this by deepening the existing game concepts (hazards, tile types, action sets) rather than through introducing completely new ones.  This helps keep the experience and strategies familiar: you’re still trying to uncover tiles as quickly as you can without overextending, and keeping paths clear for backtracking and regrouping, but the context surrounding these mechanics has shifted.  Solving the modified puzzle is interesting and fun.

So what do the expansions look like?



Games like Sub Terra usually have discoverable item cards of some sort, so their absence definitely stands out.  Their omission from the base game was partly due to limiting complexity (the base game simply didn’t need them), and partly due to theme (things are supposed to deteriorate as you play, not get better by discovering cool things – this isn’t a dungeon crawl!).

As implied above, expansions don’t have the same constraints.  Mixing in a little more complexity and bending the experience slightly are desirable!  Thematically, setting the expansions after the events of the base game gave a plausible reason why there are suddenly items in the cave: they’re lying on the cave floor next to the bodies of your friends who didn’t make it out of here last time around.  (“R.I.P., Steve.  Can I have your stuff?”)

There are fifteen item cards in this expansion.  Some give you one-shot versions of other cavers’ special abilities, others give you more generic bonuses, and others have effects that are completely new.  They’re powerful and can give you a lot more options during play, but they’re balanced by the item tiles that provide them being mainly dead ends, forcing you to backtrack with your awesome loot.

To quickly kickstart your item adventures, the Agent starts with three item cards, and has an ability to recover spent items after they’ve been used.  This gives her a lot of flexibility to play various hybrid roles in your team, even during the same session!

Finally, to stop you feeling too safe, Investigation also gives you three new Doom hazard cards.  These do nothing on the turn you reveal them, but they cause the next hazard card drawn to be resolved an additional time.  Doomed turns are extra-dangerous, so you might want to end them in a safe location more than you usually would (…if you can…).  These add a nice shiver of apprehension to the hazard phase.


Most horror games are action-oriented, and focus on fighting monsters more than surviving the environment.  Sub Terra is trying to be something different – the few monsters we have are designed to push you into bad situations rather than be something that you should face directly.  The situation as a whole is the thing that’s supposed to be scary, not the individual critters.

However, everyone’s tastes are different.  So, for those of you who want more monsters, this expansion adds more monsters!  Leapers are spawned by new hazard cards, and move twice as fast as regular horrors.  When they catch you, they cause you to lose two health points (instead of the insta-kill of their slower brethren).  While they’re harder to run away from, you have the option to deal with them by healing back to three health points and facing them head on – though as this will drop you down to dangerously low health, be careful where you’re standing when you do so.  To compensate for the additional gribblies, new tiles make the cave a bit more open, and there’s also a new Sanctuary tile which horrors cannot enter.

If you don’t feel up to wrestling leapers in close combat, you might be interested in the Mercenary.  She can fortify herself on a tile, which allows her to destroy all horrors that would enter that tile as long as she remains in place.  This is much more defensive than the Bodyguard’s Repel ability, and is a good counter to groups of horrors or a way to handle them without needing to approach.  She can also Reveal tiles at twice the normal rate, which makes her a capable explorer.

Finally, Extraction provides an optional gameplay challenge mode. Here, you must transport three biological sample containers back to the surface – you cannot win unless they all leave the cave.  The catch?  Each container you hold reduces your skill check rolls by one, which makes you worse at a number of different tasks and more likely to lose health.  Who should hold the containers?  Should you divide them up, or should one caver carry all of them?  How much support do the carriers need?


The centerpiece to Annihilation is the new gameplay mode.  Rather than start in the middle of cave and try to escape it, you’re going back in to try to destroy it.  From the exit tile, push into the cave to deliver three bombs to three special tiles, then get back out again before they explode.

Despite sounding like this drastically breaks the game, the same core concepts of rapid exploration, risk-taking, and keeping pathways clear are still present.  Layered on top of this is an additional coordination problem: where do the bombs need to be, who needs to explore, who needs to secure the escape route, and so on.  The strategies from the base game are gently stretched in a few different directions: certain characters change their roles slightly, and the threat level of certain tiles shifts a little.  It’s a refreshingly different yet recognisably familiar puzzle, and I’m very proud of how it turned out.

To help you succeed, Annihilation gives you the Exterminator.  He allows you to block tiles from spawning new horrors, which is invaluable for securing areas near the bomb sites and keeping your return journey monster-free.  Additionally, he’s the only character who is completely immune to gas, which makes him a very resilient explorer and rescuer.  Under his menacing and unfriendly exterior, I’m sure he has something approximating a heart.  Give him a spot on your team and find out!


And with that, this series of development posts comes to an end.

All that remains now is the Sub Terra Kickstarter itself, which goes live tomorrow at 8am GMT on the 10th of January.  I hope you’ll finally be able to get your hands on the game!

Many thanks to Peter and the ITB team, our artists David and Zak, and our talented legion of playtesters who have all shaped this stupid idea into something amazing.  I’m incredibly proud of what we’ve made.  It’s time for Sub Terra to escape this cave, or die trying…

Tim Pinder

Tim Pinder

Game Designer, Sub Terra

Indie gamedev robot. All opinions, fatalities and apocalypses are the responsibility of my creators, who should have worked harder on the control problem