Compiled Conversion Methods 2: D&D Adjacent to BRP

Converting To BRP From D&D Adjacent.

This method is closely based on an AD&D to RQ conversion document, the broader provenance of which I do not know.

First, find the average score for each characteristic and then divide by 3.5 to determine how many d6 to roll for it. 

This often results in a remainder to use as a + to the roll. I either round to a whole number or use a +3 or +6 mod, even if this means altering the average, or map it to the dice and adds used for an existing monster with approximately the same average.

After tweaking, you may end up with a new average. Don't worry about it.

• STR: 6 + max damage of main non-special melee attack; strongest natural attack, for preference.
• If STR is given for an AD&D monster, 18/01-75 is BRP 19, 18/76-00 is 20, and add 2 to any AD&D STR >19 to get BRP STR.
• Other system shared stats can be ported, with WIS mapping to POW and CHA to APP (for convenience).
• CON: 10 + Hit Dice (ignore plusses).
• SIZ: you have options
• the existing size class: T=1; S=2-4; M=5-17; L=18-36; H=37-61; G=62+. It's easy enough to just use the median of these ranges as the average, but remember SIZ 18 is a hulking brute of a Human, but not much of an Ogre.
• if the description includes weight, this can be compared to existing SIZ charts in CoC and RQ.
• find a rough size equivalent in BRP and use that average.
• INT: if sapient, add 1 to the AD&D Intelligence (or the median or top-end of its range); otherwise, the monster has 'fixed INT' - the same for all members of the species/type.
• POW: 9 + half Hit Dice. 
• DEX: average 10.5 (3d6), but more or less if you think there is a good reason, based on your concept of the monster or explicit/implicit in its description/abilities.
• Damage Bonus, Hit Points, Magic Points: these are all derived from the characteristics.
• Move: compare with a Normal Human; this is how it's done for system agnostic material, anyway.
• Armour Points: simple conversion - equal to AC bonus (or 10 minus descending AC), but if a good AC is from speed and agility, it might be better to give it % in Dodge instead. Lots of unarmoured monsters make sense just to be unarmoured (no AP) when converted, while for others you might want to give a narrative reason for their damage reduction.
• Attack: because this is old school, the calculation is: 20-thac0, multiply by 3, add that to 30%.
• I suppose the newer school method could be BABx3 or x5 + 30.
• In both cases, round and tweak if it doesn't feel/look right to you, and you can always pluck something from an existing source if that seems suited.
• Damage: can be used unchanged, or find a comparable monster attack if it doesn't look right in context.
• Skills: percentile abilities, like Thief skills, could be ported straight over; others can be derived from the characteristics (x3 or x5 is common, though this will need to be scaled back for some monsters).

Further Elaboration.

• Unsatisfactory Characteristics: yes, some conversions are going to look like very different monsters to the source material, so you either go with it and redefine the monster, or you tweak it until it feels right.
• I find I start to deviate from the raw numbers generated quite quickly with this method (they are a lot messier than the existing statblocks), as I'm either carrying a pre-conceived monster concept, or start to see an interesting alternative emerging.
• Incomplete Creatures: lacking one or more characteristics has mechanical/narrative effects in RQ III (and, less explicit, in CoC 5e); compare the original monster with something similar in the target system (as I did with the Gelatinous Cube).
• Special Abilities: lots of these will port straight over, and see Special Attacks in the BRP to D&D conversion above; the Damage Bonus is a useful dice pool to use for special attacks if the original numbers don't feel/look right.
• Spell-like Abilities: these will cost magic points=spell level equivalent to use, unless their daily limit makes more sense for the concept. They don't need to be mapped to existing spells in the target system, but you can do this if you like.
• Sanity Loss: this is just fun; use the guidelines in the rulebooks or pluck from an existing monster you think of as a comparable threat or with similar habits.

Sample POW ranges.

POW derived from Hit Dice is often unsatisfactory, because a mundane 10 HD Elephant will end up with a higher POW than a magical 1/2 HD Brownie, and the Brownie needs those magic points much more.

So here are some suggestions to use instead of the HD to POW conversion method.

• Normal animals: 2d6 to 3d6 (Wolf, Boar, Horse, Bear).
• Most monsters: 3d6 (Normal Humans included).
• Magically-inclined kindreds/monsters: 2d6+6 (Serpent People, Ghouls, Elves).
• Strongly magically-inclined: d6+12 (Drow, Mind Flayers, Githyanki).
• Undead will either have 1 or no POW (though this is a feature of CoC and RQ, and you can ignore it).
• 4d6 and more is appropriate for a whole swathe of D&D adjacent beasties; POW, amongst other things, is how resistant to and/or able to use magic/spell-like abilities a creature is.