コリオリス対エイリアンRPG：宇宙ホラーとアラビアンナイトSF比較

クイックアンサー

サバイバルホラー、カウントダウンクロック、そして悲惨な死の可能性が高いゲームを求めるなら、Alien RPGを選びましょう。政治的陰謀、交易、そしてアラビアンナイトに着想を得た生活感のある舞台で、危険がよりゆっくりで個人的なものを求めるなら、Coriolis: The Third Horizonを選びましょう。どちらもFree LeagueのYear Zeroエンジンを使用しているため、本当の決め手はルールではなくトーンです。

Coriolis: The Third Horizon と Alien RPG はどちらも Free League の宇宙 RPG で、Year Zero エンジンのバージョンで動作します。その共通の DNA が、比較をより鋭く、より明確にしています。ダイスプールを除いて考えれば、あなたはテーブルで非常に異なる二つの約束の間で選択していることになります。一つは宇宙での幽霊屋敷の物語。もう一つは、広大な派閥主導のサンドボックスです。

この比較は、各ゲームがグループに実際に求めるもの、つまりセッションごとにプレイヤーが何をするか、ルールがどれほど致命的に感じられるか、ゲームマスターがどのようなキャンペーン準備を引き受けるかに焦点を当てています。次の6か月をどこで過ごすかを決めるなら、以下のトレードオフが判断を明確にしてくれるはずです。

トーンと前提：恐怖と陰謀

エイリアンRPGは、映画特有のホラー（孤立したクルー、企業の圧力、交渉しない脅威）を中心に構築されています。公開されているシナリオは、プレイヤーを閉鎖的で緊張感の高い状況に置く傾向があり、問題が起こるかどうかではなく、どれだけ速く起こるかが問われます。この焦点は、ナイフで切れるような緊張感を好むグループには強みですが、長期的な政治的プレイを求めるなら限界があります。

Coriolis: The Third Horizon takes the opposite approach. The setting is a cluster of star systems shaped by faith, trade, and old rivalries, with a strong Middle Eastern and North African aesthetic rather than the usual Western space-opera defaults. Campaigns often revolve around a ship, a crew, and the deals they make. Horror exists, but it is one flavor among many.

• If your group argues about who gets the last escape pod, Alien RPG is already speaking your language.
• If your group argues about who owes whom a favor, Coriolis is the better fit.

Rules and lethality at the table

Both games use dice pools of base dice and skill dice, and both let you push a roll for a better result at a cost. In Alien RPG, that cost is often stress, and stress feeds back into the dice in ways that can spiral. The system is designed to make characters fragile and decisions heavy. Combat is fast and punishing, and a single bad round can end a character.

Coriolis uses a similar push mechanic but with a different currency: you can reroll by taking a Darkness Point for the GM, which builds a pool the GM spends to complicate the crew's lives. It is less immediately lethal and more about accumulating trouble. Characters are still mortal, but the game gives you more room to negotiate, scheme, and retreat.

• Alien RPG rewards players who plan exits before they need them.
• Coriolis rewards players who keep a favor in reserve for when the GM spends Darkness Points.

What a campaign actually looks like

An Alien RPG campaign is usually a sequence of jobs or missions, each with its own pressure cooker. The game supports this well, and the cinematic mode is explicitly built for one-shot survival horror. A long campaign is possible, but the tone tends to stay grim, and character turnover can be high. That is a feature for some groups and a dealbreaker for others.

Coriolis: The Third Horizon is built for a crew with a ship and a route. Trade, exploration, faction politics, and personal agendas all have room to breathe. The Third Horizon guide material expands the setting's factions and mysteries, which gives a GM plenty of hooks without requiring a single metaplot. The trade-off is that the game asks more of the GM up front: you need to decide what the crew is chasing.

• Alien RPG is easier to run as a pick-up game or a short arc.
• Coriolis rewards a session zero where the group agrees on a ship, a home port, and a shared goal.

Where the Free League catalog helps

Both games sit in a broad Free League space RPG lineup, and the supporting products matter for the comparison. Alien RPG has a strong line of supplements and scenarios that lean into its horror premise. Coriolis: The Third Horizon has setting and campaign books that deepen the cluster's politics and mysteries. If you already own one, the other is not redundant: they scratch different itches.

A practical way to test the waters is to run a one-shot in each before committing to a campaign. Alien RPG's cinematic scenarios are designed for exactly that. For Coriolis, a single job with a ship, a patron, and one faction breathing down the crew's neck will tell you whether the table wants that kind of long game.

• Run Alien RPG first if your group is new to horror and wants a contained experience.
• Run Coriolis first if your group likes to talk its way out of trouble.

Trade-offs to weigh before you choose

• Lethality versus longevity: Alien RPG is built for high-stakes, high-mortality play, which makes every session tense but can burn through characters fast. Coriolis is less immediately deadly and better suited to a long campaign with the same crew. Pick Alien RPG for a short, sharp arc. Pick Coriolis for a campaign you want to run for a year.
• GM prep burden: Alien RPG scenarios often come with a clear structure and a ticking clock, so prep is contained. Coriolis gives you a sandbox and expects you to decide what the crew is chasing, which is more work up front but more freedom later. If you are a new GM, Alien RPG is the gentler on-ramp. If you like building factions and maps, Coriolis pays off.
• Player buy-in: Alien RPG asks players to accept that their characters may not survive, and to enjoy that pressure. Coriolis asks players to invest in a setting with its own cultures, faiths, and politics, which is a different kind of commitment. Ask your group which pitch excites them more before you buy either book.

Products that support each side of the comparison

• Star Trek Adventures - Second Edition - Starter Set: A starter set for the Star Trek Adventures roleplaying game, taking you to the final frontier to explore strange new worlds and encounter alien life-forms. If your group wants optimistic exploration rather than horror or intrigue, this is the third option worth considering before you commit to either Coriolis or Alien RPG.
• Achtung! Cthulhu 2d20: Shadows of Atlantis 2d20 Edition: A globe-spanning adventure that takes you from the dawn of the Secret War to the fall of ancient Atlantis, beginning with the mysterious disappearance of Dr. Botho Ehrlichmann in the summer of 1939. If you like the idea of cosmic horror but want a historical rather than space setting, this adventure shows how the same dread can play out on Earth.

Which game fits your table?

Best for

• Groups who want survival horror with a clear, escalating threat and are comfortable with character death.
• Game Masters who prefer structured scenarios and a contained prep loop.
• Players who enjoy resource management under pressure, including stress and panic mechanics.

Not for

• Groups who want a long-running campaign with the same characters and a slower burn.
• Players who prefer negotiation, trade, and politics over immediate physical danger.
• Tables that dislike horror tropes or want a more optimistic tone in their space RPG.

Coriolis: The Third Horizon and Alien RPG are not competitors so much as two different moods from the same publisher. If you want dread, pick Alien RPG. If you want a crew, a ship, and a cluster full of debts and secrets, pick Coriolis. Run a one-shot of each if you can, and let the table decide which one it wants to live in.