Hostile Sun RPG Playtest

Players learn about Alchemy and uncover explorers on the strange moon that is infested with Moon Mason Bees

Playtesting and Rules Updates

Under a Hostile Sun Playtests on Youtube

  • Under a Hostile Sun is being refined through playtesting.  If you want to see the playtesters in action, check out our YouTube channel.  
  • Much has been learned and much has been adjusted.  The link on the home page connects to the newest ruleset and of course any updates are also on
  • Some of the pages on this site might still reflect older rules.  These will be updated soon.  

Rules Errata 

  • Opportunity is now handled with a dice roll at the end of each round – the size of which changes depending on round number and the environments risk level.
  • Movement is now done with squares instead of hexes.   Characters have better movement rates than before.  
  • Alchemy and creature rules have been heavily revised and streamlined.
  • There are now six character Archetypes – the Aerospace Doctor, the Priest of the Immutable, the Roboticist, the Smuggler, the Beast Rider, the Hallowed Hunter and the Chemist.  
  • Pets consist of a Buff given to the tamer, stat pools that can be spent to allow the tamer to reroll a check with the corresponding stat, a Food Resource that is used to refresh that stat pools and a conversion to an elite currency the pet can perform if given the correct resources.  



  • All images in the rulebook are now made with Photoshop and licensed stock images or hand drawn images.  


Rulebook Updates

  • Several images not included in the original publication have been added and more are on the way. These include digital image assets made with Adobe Photoshop and Unsplash (two examples of these shared above and below), cartoons made with Adobe Fresco and two added AI images (both of which required evolutions and edits from multiple AI outputs in photoshop – these are the images of the red-haired Astronaut on 9 and the Eye Creature on p17)
  • Grammer errors and “Replace All” errors fixed. Notecard reference adjusted to reflect most current version of rules.
  • The project page now has a character sheet in word format – it is prefilled with a sample character made by one of my players involved in playtesting. The word doc also has explicit places to type current amount of the basic game resource currencies.
  • I remain sad about the attempt to hurt 3rd party d20 RPG Developers.  Please support the Open RPG Creative License (ORC), Creative Commons RPG Systems and Project Black Flag
  • Hostile Sun has a Creative Commons SRD
  • For the 12 Word RPG Jam a 12-Word Version of the game was created.  

Red Haired Woman in space suit on red planet in outer space

Playtest Update

Randomly rolled stats can get pretty imbalanced. (This has come up in the early playtesting) That can be either a bug or a feature depending on the game you’re playing.  If you want to prevent to wide an imbalance:

  1. Pick a starting number of points for players to distribute – higher or lower depending on intended difficulty.
  2. Have the players generate their stat values. Set max stat value to 16. If there is more than one value that is 16 or greater reduce those values to 14. Any values lower than 8, increase to 8
  3. Reveal that the player with objectively the worst stat block will uncover a mutation in the course of playing. I plan to write explicit rules for this in the first supplement to the core rulebook

“Fairy tales do not tell children the dragons exist.  Children already know that dragons exist.  Fairy tales tell children the dragons can be killed.” – Quote on Hope and Storytelling from G.K. Chesterton

Character Creation Page