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What if we overlayed D&D 3.5 rules on top of T20 in the OTU?

Werner

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This is an alternate reality OTU that splits off from the main timeline in 1103 Imperial when magic and gods are suddenly unleashed for some unexplained reason. Everybody gains one level in a D&D 3.5 class, players get to choose which class it is according to what their ability scores are best suited for. Characters with high intelligence scores can become first level wizards for example. The change occurs when they are in their sleep, they dream they are a fantasy character, a wizard, a fighter, a cleric, a rogue whatever, then they wake up and discover they have those dream character's abilities, they are still their old selves and character classes. A lot of people just gain a level in fighter and pick up feats in archaic weapons, but are otherwise non-magica. Technology still works of course. Hit points are substituted for stamina and Lifeblood. Everyone is a 1st level D&D class in addition to whatever they were before.

How does this affect the setting? Remember everyone starts out as a 1st-level D&D class, so for a time there will be no second level anything until they advance.
 
If you start from the T20 assumptions, most everyone will have levels in something already. The T20 classes are purposely toned way down from the D&D norms, so adding a fantasy PC class level is going to be a turbocharge almost without exception.

D20 fantasy has dabbled in space settings before, though mostly under 3.0
 
If you start from the T20 assumptions, most everyone will have levels in something already. The T20 classes are purposely toned way down from the D&D norms, so adding a fantasy PC class level is going to be a turbocharge almost without exception.

D20 fantasy has dabbled in space settings before, though mostly under 3.0

I am sure there would be political chaos within the Imperium and without. Also some spells, such as teleport, don't have range limits, one could teleport across Interstellar distances, since the whole OTU would count as a single "prime material plane".
 
some spells, such as teleport, don't have range limits, one could teleport across Interstellar distances, since the whole OTU would count as a single "prime material plane".

Assuming all of D&D's cosmology transferred as well. It might take centuries for the high level spells to appear, since the tradition of magic would largely be starting from scratch.
 
Assuming all of D&D's cosmology transferred as well. It might take centuries for the high level spells to appear, since the tradition of magic would largely be starting from scratch.
Yep, and alignments start showing up as well, maybe we could convert Jump Space to the Astral Plane and have random encounters. Same rules for getting to the Astral plane as getting to Jump space, same amount of time you spend in Astral space as you do in Jump space. You can jump parsecs or travel to the outer planes.

Funny think about the Astral Plane is, you don't need a space suit to survive in it, due to its timelessness, if you blow a hole in a Starship, it won't depressurize until you reenter normal space. You also don't need to breath, or eat in Astral space, your bodily functions resume upon entering normal space.
 
Yep, and alignments start showing up as well, maybe we could convert Jump Space to the Astral Plane and have random encounters. Same rules for getting to the Astral plane as getting to Jump space, same amount of time you spend in Astral space as you do in Jump space. You can jump parsecs or travel to the outer planes.

Funny think about the Astral Plane is, you don't need a space suit to survive in it, due to its timelessness, if you blow a hole in a Starship, it won't depressurize until you reenter normal space. You also don't need to breath, or eat in Astral space, your bodily functions resume upon entering normal space.

The Astal Plane in D&D isn't timeless. It's time is percieved as being much slower, but that hole WILL leak. If it would take 1 minute to empty in N-Space, it's 1000 minutes in Astral.

(Timeless would preclude movement at all.)
 
The Astal Plane in D&D isn't timeless. It's time is percieved as being much slower, but that hole WILL leak. If it would take 1 minute to empty in N-Space, it's 1000 minutes in Astral.

(Timeless would preclude movement at all.)

Good point, so the crew has 16 hours and 40 minutes to patch it up, and I believe the Astral Plane sustains life anyway, movement through it is by thought, for the purpose of this setting, we'll treat the Ship's computer as a thinking entity, and it is thinking of plotting a jump to its destination, and the astral plane delivers it to its destination as if it were in jump space. There are other ways to travel in jump space as well using magic that does not require following the rules to enter jump space. Fortunately for merchants the sort of magic required to enter the astral plane is at higher levels than first.

Plane shift is a 5th-level clerical spell, it can get you into the astral plane with 8 other people. Astral projection is a 9th level clerical spell (3.5 edition by the way) a cleric can cast planeshift at 9th level

Plane shift is a 7th level wizard/sorcerer spell, a sorcerer can cast this at 14th level, a wizard at 13th level. Starships won't have competition for some time yet, and anyway in fantasy worlds people still travel by sailing ship and on the back of a horse, so I suspect starships will remain in business.
 
True, or near true, perfect timelessness opens other cans of worms as well. The two Oceans Unmoving sequences of Sluggy Freelance are an interesting take on the idea, as well as some of those worms.
 
True, or near true, perfect timelessness opens other cans of worms as well. The two Oceans Unmoving sequences of Sluggy Freelance are an interesting take on the idea, as well as some of those worms.

Well it's a magical plane, its doesn't entirely have to make sense, it would be interesting if electronics didn't work in this plane, nor chemical reactions, so a Starship using this sets the jump up, enters the astral plane and everything onboard shuts down and goes dark. Fortunately the characters don't need life support, they can continue to exist for as long as it takes. Mechanical weapons do work, as do muscles, bows and arrows, crossbow, swords spears and the like, and creatures in the astral plane also have their natural weapons as well. The astroplane Carrie's the Starship to its preprogrammed destination and then releases it back into normal space at the chosen destination, assuming a misjump did not occur. A jump bubble is maintained within the astral plane, one can pass through the boundary of the jump bubble and it feels like a slight static discharge as one passes through, any creature or object that enters the Ship's jump bubble at the time the ship is about to exit the astral plane with go with that ship. Any creature or object that is not will be left behind in the astral plane and will have to find another way out. A creature that is within the jump bubble but outside the hull of the ship will find himself in the vacuum of space when the ship enters normal space!
 
d20 Modern and d20 Traveller are partially compatible, but not plug-and-play. Here's a breakdown of where they align and where they differ:




✅


  1. Core System:
    • Both use the d20 System (based on D&D 3.x), so they share mechanics like:
      • d20 roll + modifier vs. DC
      • Ability scores (STR, DEX, etc.)
      • Base attack bonus (BAB)
      • Feats and skills
  2. Combat Mechanics:
    • Turn-based combat with initiative, armor class, hit points
    • Similar action economy (move, standard, full-round)
  3. Feats and Skills:
    • Many feats and skills from one can be ported to the other with minor tweaking



❌


  1. Character Classes:
    • d20 Modern uses basic classes (Strong Hero, Fast Hero, etc.) and advanced/prestige classes
    • d20 Traveller uses a career-based system (e.g., Scout, Mercenary) tailored to the Traveller setting
    • Direct class swaps don’t work without rebalancing
  2. Tech and Equipment:
    • Traveller assumes far-future sci-fi (starships, TL 10–15 tech)
    • d20 Modern is mostly contemporary or near-future
    • Weapon stats, armor, and gear aren’t 1:1 and need conversion
  3. Psionics vs. Tech:
    • d20 Modern might use magic or psionics (Urban Arcana), while d20 Traveller leans into hard sci-fi
    • Compatibility here depends on tone and setting
  4. Currency and Wealth System:
    • d20 Modern often uses the Wealth bonus system
    • Traveller uses credits and detailed economics
  5. Starships and Space Travel:
    • Traveller includes detailed ship-building, travel, and trade rules
    • These don’t exist in d20 Modern and would require importing subsystems wholesale



🛠️


If you're aiming to merge the two:


  • Use d20 Modern for core mechanics and character building
  • Import Traveller’s setting, equipment, starships, and careers as flavor/background
  • Convert Traveller NPCs and ships to d20 stat blocks
  • Adjust Wealth or credits for consistency
  • Decide whether to include Traveller’s aging and career progression system



🧩 Optional Alternative​


If you want an easier bridge between d20 Modern and sci-fi play, consider d20 Future (an official supplement to d20 Modern), which includes:


  • Starships
  • Cybernetics
  • Mecha
  • Mutants
  • Alien races

You could then flavor the campaign using the Traveller universe, while running mechanics off d20 Modern + d20 Future.



 
Here’s a cheat sheet comparing d20 Traveller careers to d20 Modern classes. This will help you translate characters or NPCs between the two systems.

🧾 Quick Guide: d20 Traveller Careers vs. d20 Modern Classes​

d20 Traveller CareerEquivalent d20 Modern Basic ClassSuggested Advanced Classes (Optional)
ArmyStrong Hero or Tough HeroSoldier, Martial Artist
MarinesTough Hero or Strong HeroSoldier, Bodyguard
NavySmart Hero or Dedicated HeroField Scientist, Techie
ScoutsFast Hero or Smart HeroExplorer, Field Scientist
MerchantsCharismatic Hero or Smart HeroEntrepreneur, Diplomat
RoguesFast Hero or Charismatic HeroInfiltrator, Negotiator
Nobility (e.g. Noble titles)Charismatic HeroDiplomat, Personality
ScientistsSmart HeroField Scientist, Techie
Technicians / EngineersSmart Hero or Dedicated HeroTechie, Engineer
Psions (if used)Dedicated Hero or Smart Hero (with Urban Arcana or d20 Future psionics rules)Telepath, Battle Mind (d20 Future)
CriminalsFast Hero or Charismatic HeroInfiltrator, Gangster
Corporate / ExecutivesCharismatic HeroEntrepreneur, Field Officer
Explorers / FreelancersFast Hero or Smart HeroExplorer, Adventurer

🛠 Key Translation Notes​

  • Basic Classes give the broad archetype (physical, mental, social). Choose based on what the Traveller character did most.
  • Advanced Classes allow you to fine-tune once the character reaches level 4+.
  • Traveller’s rank and career terms (e.g., Ensign, Captain) are background/flavor in d20 Modern but can suggest prestige levels.

💡 Example Conversion​

Traveller Character:
  • Career: Scout
  • Skills: Astrogation, Survival, Pilot, Recon
  • Rank: Senior Scout
d20 Modern Version:
  • Basic Class: Fast Hero (for mobility and recon)
  • Advanced Class: Explorer (for travel and survival expertise)
  • Key Skills: Navigate, Pilot, Survival, Spot, Move Silently
  • Equipment: Adapt Traveller gear to d20 Future equivalents (or homebrew stats)

 
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