Metamorphosis Alpha & D&D
Who else mixed a little Metamorphosis Alpha (MA) into their AD&D games? It was one of the first things we tried back in the day. Yeah, the systems didn’t mesh all that well—but since when did “rules” ever stop a bunch of 13-year-olds?
MA was actually the first RPG I ever bought, and that photo shows my original copy (check out that $5 price tag).
The two systems are similar in some ways but disparate enough to give GMs a headache. James Ward put out some conversion guidelines in Dragon Magazine, but I never cared much for them. So here’s my own take that’s a little more structured than what my 13-year-old self would have used.
Converting Metamorphosis Alpha (MA) to Dungeons and Dragons (D&D)
Don’t try converting between the two systems on the fly—it’s more trouble than it’s worth. Since D&D is the dominant system, it’s easier to convert MA mechanics into D&D rather than the other way around.The MA rules are super loose like those in OD&D so GMs will have to stay on their toes to fill in the blanks as needed. When in doubt, default to D&D rules.
Attributes
Pretty straightforward except Radiation Resistance which we’ll cover below.
| D&D | MA |
|---|---|
| Strength | Strength |
| Dexterity | Dexterity |
| Constitution | Constitution |
| Intelligence | Mental Resistance |
| Wisdom | Mental Resistance |
| Charisma | Leadership Potential• |
- For non-pure strain humans roll 2d4+1 for charisma.
Levels, Hit Points, & Saving Throws
MA characters don’t have levels—instead, they gain 1d6 hit points per point of Constitution. They also lack any variation in combat ability. To seamlessly integrate them into D&D, let’s keep things simple:
- They retain their rolled hit points.
- They function as Fighters for combat and saving throws.
- Their level is determined by CON ÷ 3 + 3, ranging from 4th to 9th level, with an average of 7th.
This does make Constitution the most important stat for MA characters, but it keeps the conversion straightforward.
Weapons
Weapons should all be based on the charts in D&D except for tech items which work as stated.
Armor Class
| Armor | OSR | AD&D | 3.5 |
|---|---|---|---|
| None | 9 | 10 | 10 |
| Heavy Fur Or Skins | 8 | 9 | 11 |
| Partial Carapace | 5 | 6 | 14 |
| Cured Hide Or Plant Fiber Armor | 4 | 5 | 15 |
| Thin Metal Armor Or Full Carapace | 3 | 4 | 16 |
| Shield | -1 | -1 | +1 |
| Duralloy Shield | -3 | -3 | +3 |
Movement
MA characters should have standard human movement speeds perhaps adjusted up or down a bit for characters with Taller or Shorter mutations. Characters with the Wings mutation can fly at 24″ in AD&D
Radiation & Radiation Resistance
Radiation is one area where I’d lean toward MA mechanics. MA has a great radiation effects table, but it’s a bit cumbersome in play. Here’s a streamlined approach that keeps the spirit of the original while making it easier to use.
Non-MA Character’s Radiation Resistance
Non-MA characters have a Radiation Resistance (RR) equal to CON ÷ 2 (round down) + 5:
- 18 CON = 14 RR
- 10 CON = 10 RR
- 3 CON = 6 RR
This makes non-MA characters less resistant—but also less vulnerable—to radiation, which makes sense given their limited exposure to it.
Radiation Intensity & Exposure
- Characters are immune to radiation with an intensity equal to or below their RR score.
- Each turn of exposure to any radiation reduces RR by 1 point.
- RR recovers with rest, at the same rate as hit points.
For example, a character with 10 RR in a Radiation Intensity 10 area takes no damage. However, even a character with 18 RR will eventually succumb to Intensity 3 radiation—it’ll just take a while.
Radiation Damage
Each turn a character is exposed to radiation above their RR, they take 1d6 damage per point of Radiation Intensity exceeding their RR.
For example, a character with 10 RR in a Radiation Intensity 18 zone takes 8d6 damage per turn!
If you want to further D&D-ify it, you can allow a saving throw vs. death (Fortitude) for half damage.
Death From Radiation Option
As a fun optional rule, characters who die from radiation can attempt a save vs. death (Fortitude) at -5. If they succeed, they survive but are deathly ill for a week. Afterward, they mutate:
- Charisma is permanently reduced by 5 (minimum 3).
- Roll for mutations and defects as normal.
This keeps the high-stakes danger of radiation while adding a classic Metamorphosis Alpha twist.
Mutations
Most of the mutations can be played right as written though some are notorious trouble makers like Time Field Manipulation, Death Field Generation, and Planar Travel. They’re the deliciously unbalanced, game upending type of abilities you found early in the hobby. They were a blast to play but could be a real headache for the GM.
QuestRex Mutations
For my own game, QuestRex, I built a mutation system inspired by Metamorphosis Alpha and its cousin, Gamma World. I leaned more toward a “biology-esque” approach, keeping mental mutations separate within the QuestRex Psionics system (though I included optional rules for mixing them if you prefer).