flotsam and jetsam for tabletop games, by quadra.

Mothership House Rules

mothership house rules mothership 0e

Mothership: House Rules! (Based on the Alpha Zine Edition, 3rd Printing rules & errata (0E). Note that these house rules are compatible with pre-1E playtesting and my playtesting character sheet. Once 1st Edition is solidified and released, this page will be updated with a 0E section and a 1E section.)

Over the course of running several Mothership one-shots and an extensive campaign, I’ve tweaked a number of things. Here are my current house rules:

Action & Combat


Aiming is now more useful than it is in the PSG (12.2): a PC may take a single action to Aim. This grants advantage on their next ranged combat roll, provided their target stays within their line of sight, the PC takes no other actions, and nothing hits the PC before they are able to make that combat roll.

Combat Rolls

I consider this one essential. If you’re only going to house rule one thing, make it this.

Instead of opposed Combat/Armor rolls, just have the attacker roll Combat. If they succeed, they roll damage and the defender may then choose to roll Armor to save for half or make a Combat roll to counterattack or make a Body roll to break free of close quarters combat. IMO this is clearer, speeds up combat a lot, and increases the rate at which people actually hit stuff.


If anyone rolls a crit success on an attack, they roll on Sean’s crit table (see page 3 of the Warden Screen). If a player rolls a crit success on a non-combat roll, I give them something nice (e.g. “you find 1d10 extra clips of ammo when searching the body”, you lose 1d5 Stress”, etc.). If they crit fail on any roll, I do something bad (and contextually appropriate) to them that significantly shifts the situation out of their favor (e.g. “your gun breaks”, the crowbar flies out of your hand and clatters across the floor”, you manage to pull the grenade off the Marine’s corpse — without the pin”, etc.)


Borrowing from James Young’s house rules, PCs may take both of their actions in a turn to attempt a Gambit: a cool, risky, and dangerous move not covered by other actions (e.g. trying to leap onto a large creature, shove a live grenade in its mouth and leap away, etc.). The Warden works with the player to determine how the player’s idea will work, and what the consequences will be if it doesn’t.

Then the player makes two Combat rolls. If both succeed, they pull it off! If they both fail, something very bad happens to them. If one succeeds and one fails, they either get a partial success, or they succeed, but at a cost. The Warden may dictate this or let the player choose.

No-Initiative Action

I’ve gotten rid of initiative altogether and replaced it with my no-initiative action system. Check the post for details, but the highlights are that action rounds (AKA combat rounds) start and end automatically whenever makes sense to the Warden, the Warden describes the evolving situation each round for players to react to, all actions are resolved simultaneously, and everyone gets one movement and one action each round (instead of two actions).

Stress / Calm

I use my d100 Calm system in place of the standard Stress system in my home campaign, which I find more suited to campaign play. If you don’t want to replace the whole Panic system but you want to make it more campaign-friendly, check out my deprecated Panic Table Rolls house rule below! For one-shot play, I still use Stress.

Gaining Stress

When using the Stress system, I dole out Stress when PCs encounter / experience something:

When using Calm, I generally dock PCs’ Calm in 1d10 increments across the board and multiply Stress numbers in modules by 2 or 3.

Healing & Relieving Stress / Gaining Calm

Instead of healing by the amount they succeed by on a Body save, Players just heal by the number rolled on the die if they succeed the save. It’s mechanically almost equivalent, and less math. Same goes for relieving Stress/regaining Calm: roll Fear and instead of relieving the amount they succeeded by divided by 10, just relieve the number on the die divided by 10.

Panic Checks

I keep forgetting when I should do Fear or Sanity checks and when I should do a Panic check, so now I just have everyone Panic Check every time they gain Stress (except when they gain 1 Stress or gain Stress from the Panic Table). This balances out my gentler Stress and Panic Table rules, I think, and is just easier to track.

Player Characters


I ask Android players which of my Android Types they want to play and use my special rules from there.


Player characters can carry a number of items equal to their Strength/10, plus 1 per hand, plus whatever they’re wearing, within reason (so a vaccsuit with magboots and a bodycam won’t count towards this). Items stack 3/slot.


Just like monsters, the PCs now have Hits in addition to HP. All classes get 2 Hits, Marines get 3. Each Hit has HP equal to the character’s Strength stat. When you take damage, reduce HP accordingly until you reach 0. Once you have 0 HP, you lose a Hit, your HP resets, and you roll on the Critical Hit Table, ignoring additional damage. An attack that does more damage than your current HP will only reduce your current HP, and will not overflow” to the HP of your next Hit. Attacks dealing MDMG deal damage directly to Hits. A Hit can only be healed with the use of a medbay.

Leveling Up

When leveling up, I’ve changed the option from cure a phobia or addiction” to cure a condition,” which include phobias and addictions but also stuff from the panic table like Death Drive.



The Bioscanner only works on the level you’re currently on, to save myself the headache of tracking baddies across multiple floors. It shows somewhat indistinct blobs and isn’t super precise.

Stat Checks

No PC ever makes the same check twice, for it is not the same check and they are not the same PC.”

When someone fails a stat check, the situation changes for the worse, proportionally to what they were attempting. Trying to hack a terminal? Now it’s locked you out. Trying to shoot someone with your SMG? Whoops, you shot the lights out and now it’s dark. Trying to shoot someone with your laser cutter? Whoops, you shot a hole in the hull and now the ship is decompressing! The idea here is to make everything consequential, and keep everything moving. It results in situations that are more cinematic and dramatic, and it means the game state doesn’t just wait for players to succeed.

Challenge HP

When a challenge should have a time pressure element (e.g. downloading data from a hacked terminal while being hunted down, trying to open a blast door while aliens are chasing you, etc.), I use my Challenge HP system.

Deprecated House Rules

Panic Table Rolls (replaced with Calm)

Players roll Stress + 1d10 instead of 2d10 for campaign games, so beloved characters won’t get heart attacked so much. 2d10 still seems good for one-shots tho.

I’ve also softened the two worst Panic Effects a bit:


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