Updated 10 February 2015 (added link to Monster Traits and Actions)
This is the third in my series of conversion documents for D&D 5th Edition. (You can find the one for Next here and the one for 3.5/3E/Pathfinder here.) I created this document by comparing the 5E versions of monsters from the Monster Manual with their 2E counterparts. I also referred to two sources for converting monsters from 2E to 3E: Wizards’ official Conversion Manual and the Dragon Magazine article “How to Create a Monster”.
I will once again include two warnings:
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If you compare the 2E and 5E versions of monsters yourself, you will
notice this conversion does not produce perfectly identical results. I went for approximation, not precision.
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I am fallible, so there may be mistakes. If you find any, let me
know.
The end of this document also explains how to adjust these guidelines for converting monsters from 1E.
You will need access to at least the D&D Basic Rules and the Monster Manual to make full use of this. The Dungeon Master’s Guide, while not strictly required, is highly recommended for its monster creation guidelines (pages 273-283).
Also, thanks to Russ Morrissey for a simplification on dragon AC, and the people in this ENWorld thread for general help!
Challenge Rating
Before you get started, you should choose an initial Challenge Rating for the creature. This is an estimate of the monster’s CR, which you can use to guide the rest of your conversion. There are two ways to do this:
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Use the CR of a similar 5E creature. If you use this approach, the
creature should also serve as your “reference monster” (see Ability Scores).
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Use the CR Estimator in Appendix 1 to convert its AD&D 2E XP Value.
When you are finished converting your monster to 5E, you may wish to adjust this initial CR for a better fit. The best way to do this is to use the rules for determining CR in the DMG, but if you’re pressed for time, you can just compare it to similar 5E creatures once again.
Size
5E appears to use 3.5’s size ranges (slightly trimmed). These do not perfectly match 2E’s size categories, so convert them as follows:
2E Size 5E Size
Tiny (2’ or less) Tiny (2 feet or less) Small (2’-4’) Small (2-4 feet) Medium (4’-7’) Medium (4-8 feet) Large (7’-8’) Medium (4-8 feet) Large (8’-12’) Large (8-16 feet) Huge (12’-16’) Large (8-16 feet) Huge (16’-25’) Huge (16-32 feet) Gargantuan (25’-32’) Huge (16-32 feet) Gargantuan (32’ or more) Gargantuan (32 feet or more)
You can also simply use the 2E size category as is, if you don’t mind being off by a few feet.
Type
2E did not have creature types, so you will need to assign those yourself, based on the monster’s description. The types are all explained in the 5E Basic Rules.
Tags
Appended to the creature type in 5E, these can be determined from the monster’s description. Typical tags include titan (for creatures like the tarrasque), shapechanger, specific types of fiends (such as demon or yugoloth), and specific humanoid races (elf, thri-kreen, etc.) If your creature isn’t likely to have any of the tags above, skip this step.
Alignment
Generally, keep this the same. However, creatures in 5E may also be unaligned, meaning they operate on instinct - so you may want to change neutral to unaligned for some creatures.
Armor Class
It’s easiest to recalculate AC from scratch, based on their Dexterity bonus and any armor worn. (Make sure to check the rules for determining AC in the Basic Rules PDF.)
If the creature did not wear armor, and had an AC of 6 or below, they should have natural armor. In that case, give them a +2 bonus to their new AC.
Dragons appear to have stronger natural armor in 5E. For now, I suggest estimating their 5E AC by subtracting it from 19.
Example: A dragon of some sort has AC -1. Subtract that from 19: 19-(-1) = 19+1 = 20.
Hit Dice
In 5E, the type of hit die is determined by a creature’s size. Tiny creatures use d4 hit dice. Small creatures use d6 hit dice. Medium creatures use d8 hit dice. Large creatures use d10 hit dice. Huge creatures use d12 hit dice. Gargantuan creatures use d20 hit dice.
In 2E, Hit Dice may be displayed in formats like “1-1” or “5+3”. The first number is the number of Hit Dice; ignore the later number.
Tiny creatures should keep the same number of hit dice as they had in 2E.
Small or Medium creatures should add one hit die. For example, 1d6 should become 2d6.
Large, Huge, and Gargantuan creatures should add two hit dice. For example, 3d10 should become 5d10.
Average hit points for creatures should be recalculated as follows:
Xd4 - Multiply X by 2.5 (round down), then add their Constitution bonus, times X.
Xd6 - Multiply X by 3.5 (round down), then add their Constitution bonus, times X.
Xd8 - Multiply X by 4.5 (round down), then add their Constitution bonus, times X.
Xd10 - Multiply X by 5.5 (round down), then add their Constitution bonus, times X.
Xd12 - Multiply X by 6.5 (round down), then add their Constitution bonus, times X.
Xd20 - Multiply X by 10.5 (round down), then add their Constitution bonus, times X.
Example: A monster has 3d8 HD and a Constitution of 14 (+2 bonus). So their average hit points are 4.5 times 3, rounded down: 13. Then you multiply their Con bonus by their HD, for a total of +6. 13+6 = 19.
Two exceptions:
Oozes should probably keep their current hit dice.
Dragons have been upgraded a lot since 2E, so any 2E dragon converted like other monsters is likely to be comparatively weak. But since we have only one example, I can only suggest you convert them like other creatures of their size.
Speed
Use the 2E Movement stat, then convert it as follows for each movement type (in feet).
Movement up to 12: Divide by 3, multiply by 10, round to nearest 10.
Movement above 12: Multiply by 2, round to nearest 10.
For reference, the 2E abbreviations for special movement are Fl (flying), Sw (swimming), Br (burrowing), Cl (climbing), and Wb (moving across webs).
Example: A creature has Movement 9, Fl 21. Its new ground movement is 9/3 = 3, 3x10 = 30 feet. Its new flight speed is 21x2 = 42, rounded to 40 feet.
A creature that can move across webs (Wb) should replace that speed with the trait Web Walker (see Giant Spider in the Monster Manual).
Ability Scores
The only ability score provided in most 2E stat blocks is Intelligence. You can use this statistic as given - if there’s a range, go for the average or highest score. If only the Intelligence “rating” is provided, use the below for reference:
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Non- (0) [which must be increased to at least 1 for 5E]
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Animal (1)
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Semi- (2-4)
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Low (5-7)
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Average (8-10)
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Very (11-12)
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High (13-14)
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Exceptional (15-16)
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Genius (17-18)
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Supra-genius (19-20)
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Godlike (21+)
If you are really lucky, the monster’s description may describe other ability scores. Use them as given if they are provided, with the exception of Strength, which should be converted as follows:
2E Strength 5E Strength
1-18 Same 18/01-18/99 18 18/00 (2E ogre) 19 19 (2E hill giant) 20-21 20 (2E stone giant) 22-23 21 (2E frost giant) 23-24 22 (2E fire giant) 25-26 23 (2E cloud giant) 27-28 24 (2E storm giant) 29 25 30
For any ability scores missing at this point, you will need to choose a “reference monster”. This is an existing monster similar to the one you’re converting. (For example, a skeletal undead could use the skeleton as a “reference”.) If you based the monster’s initial CR on an existing 5E monster, you already have your “reference monster”!
Use the ability scores of the “reference monster” to fill in any blanks, possibly tweaking them as needed to fit the monster’s concept or known ability scores.
When choosing a “reference monster”, use these sources, in this order of preference:
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The D&D 5E Monster Manual.
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Monsters from D&D Next material.
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D&D 3.5’s Monster Manual. You can use this site as a quick
reference: http://www.d20srd.org/indexes/monsters.htm
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The “How to Create a Monster” article (linked above).
Note that in 5E, creatures always have all six ability scores. If you use a 3.5 “reference monster” and it is missing any of these, you should look at the next closest Next or 5E monster, or use the guidelines for filling in blanks from my 3.5 conversion document.
Alternatively, the 2E sourcebook Dungeon Master Option: High-Level Campaigns provides a method for determining monster ability scores, if you want to fill in the blanks from the 2E side. They recommend rolling randomly and consulting a table, but I would use the average result on the table instead (results 9-12). Another 2E resource to consider is The Complete Book of Humanoids. Note that any resulting Strength scores would still need to be converted to 5E.
Saving Throws
Ignore the 2E rules for monster saving throws. In 5E, saves are associated with each of the six ability scores, so most creatures just use their ability bonus for saves.
However, a few 5E monsters do appear to apply their proficiency bonus to these saves. You may wish to do the same for your converted creature, if their 2E description suggests it should.
In most cases, though, you should probably pass on giving your creature proficiency with saves - it’s much easier without it.
Skills
The majority of monsters will have few or no skills, especially monsters driven by instinct. Consult the 2E monster’s description to see if it has any talents that might match a particular 5E skill. For reference, the 5E skills are:
Athletics (Strength)
Acrobatics, Sleight of Hand, and Stealth (Dexterity)
Arcana, History, Investigation, Nature, and Religion (Intelligence)
Animal Handling, Insight, Medicine, Perception, and Survival (Wisdom)
Deception, Intimidation, Performance, and Persuasion (Charisma)
Full descriptions of the skills can be found in the Basic Rules PDF.
If a creature has proficiency in a skill, their bonus with that skill is equal to the relevant ability bonus, plus their proficiency bonus.
Example: A monster has a Dexterity of 15 (+2 bonus) and proficiency in Stealth. This means that they should have a +4 bonus with Stealth (Dexterity) checks. If they are a more powerful creature, they may have a +5 bonus instead.
If a creature is hard to surprise, it should probably have proficiency in Perception (Wisdom). If the creature is good at surprising enemies, it should probably have proficiency in Stealth (Dexterity).
Some creatures seem to have a higher proficiency in one skill than the others, typically double their normal proficiency bonus (+4 or +6). For example, doppelgangers have a +4 on Deception (Charisma) checks. You may wish to do the same with a creature’s “signature” skill.
Vulnerabilities, Resistances, Immunities
Look at the 2E creature’s Special Defenses and description - this should give you an idea what the creature is vulnerable against (listed under Damage Vulnerabilities in 5E), what the creature is resistant against (listed under Damage Resistances), and what the creature is immune against (listed under Damage Immunities or Condition Immunities).
Some 2E creatures can only be harmed by magical weapons of a certain bonus (+1, +2, etc.). This should be listed under Damage Resistances as follows:
bludgeoning, piercing, and slashing from nonmagical weapons
If the creature can only be harmed by some other material, add the following:
...nonmagical weapons that aren’t (silvered or adamantine or [other substance])
Modify the above as needed for other resistances.
When you note Condition Immunities, remember that they may overlap with resistances or damage immunities. For example, a creature immune to poison damage should also note that they are immune to the poisoned condition.
The innate immunities of undead in 5E are:
Damage Immunities: poison
Condition Immunities: poisoned
Only add other immunities to an undead creature if they are separate from its undead nature.
Incorporeal creatures should probably have the following resistances and immunities:
Damage Resistances: acid, cold, fire, lightning, thunder; bludgeoning, piercing, and slashing from nonmagical weapons
Damage Immunities: poison
Condition Immunities: grappled, paralyzed, petrified, poisoned, prone, restrained
Magic resistance has also been simplified, and is now listed as a trait - see the flameskull for an example.
Senses
There are only four senses established in 5E at this point: blindsight, darkvision, tremorsense, and truesight. 2E’s infravision, ultravision, and similar senses are equivalent to darkvision. Any non-visual replacement for sight should be blindsight or tremorsense. Any creature with innate “true seeing” should have truesight.
Also, all creatures have a passive Perception score. This is equal to 10 plus their total bonus to Perception (Wisdom) checks.
Languages
Refer to the Basic Rules PDF for the known languages in 5E. If no language for your creature is listed there, give them the native language provided in their 2E description.
Traits
To determine a creature’s Traits, look at the 2E monster’s description. When possible, you should use equivalent traits from the Monster Manual; if this is not possible, either base the converted trait on a similar 5E trait, or simply use the original text as is.
A list of the known Traits in 5E can be found here.
Spellcasting is a special case. In addition to being used for 2E monsters with levels in a spellcasting class, lists of spell-like powers also tend to be translated as Spellcasting. (The only exception should be specific spell-like powers which are really important to a creature’s concept, in which case they are either listed as Innate Spellcasting or broken out as individual traits, actions, or reactions.)
If the creature lists a caster level, use that. If no caster level is provided, use their 2E Hit Dice. Make sure to use the 5E rules for spellcasting, and replace spells with closest equivalents if necessary; refer to the Basic Rules for more details. (For Innate Spellcasting, the spellcasting ability is typically Wisdom or Charisma.)
Actions with an Attack Roll
Actions should be taken from a 2E creature’s normal attacks, Special Attacks, or description. You need to convert three things to make these into 5E actions - the “to hit” bonus, the damage inflicted by elements of the attack, and any saving throws required.
A list of the known Actions in 5E can be found here.
To Hit
Ignore the THAC0 and recalculate this from scratch. In 5E, the “to hit” for an action is based on the proficiency bonus. This is combined with the relevant ability bonus (usually Strength or Dexterity).
Note that most natural attacks (claw, bite, etc.) appear to be finesse attacks, meaning they can use either Strength or Dexterity with attack rolls. Unless you think your creature should be a weak melee combatant, you should choose the highest of either Strength or Dexterity for “to hit” with natural attacks.
Unusual attacks like the wraith’s Life Drain appear to either have a higher bonus, or are using something other than Strength or Dexterity. I don’t have any specific recommendations for this right now, but feel free to experiment with other ability scores (like Constitution or Charisma) if that seems appropriate. You’re probably safer avoiding that, however.
Damage
In 2E, damage is often expressed not in dice, but as a range, like 1-6, 3-12, or 2-5. In such cases, you will have to figure out how many dice that is before converting. (In the above cases, it’s 1d6, 3d4, and 1d4+1.)
For attacks that use a weapon, refer to the damage listed in the Basic Rules PDF or Starter Set. If the creature is large, increase the weapon’s damage die by one (i.e. 1d6 becomes 2d6). If the creature is huge, increase the weapon’s damage die by two (i.e. 1d6 becomes 3d6). Some especially huge creatures, and gargantuan creatures, may increase the damage die by three (i.e. 1d6 becomes 4d6), but you may be safer sticking with two.
For natural attacks by tiny or small creatures, you should probably leave the damage dice alone. However, the minimum damage die appears to be 1d4, so any weaker attacks should probably upgrade to that. (The same goes for damage dice below 1d4 for other creatures.)
For natural attacks by medium or larger creatures, use the following table:
2E Damage Dice 5E Damage Dice
1d4 1d6 (or 2d4) 1d6 1d8 (or 2d6) 1d8 1d10 (or 2d8) 1d10 1d12 (or 2d10) 1d12 2d8 (or 2d12)
If an attack inflicts more than one die of damage, increase the 5E damage die by that number. For example, 2d4 should become 2d6 (or 3d4).
Some creatures’ strongest natural attacks seem to add both one die of damage and increase the die type by one - for example, 1d6 becoming 2d8. This should be used carefully, however, and shouldn’t be used on more than one attack.
Don’t forget to add the monster’s Strength bonus to melee damage and Dexterity bonus to ranged damage. You can calculate average damage through the method above under Hit Dice.
Other types of damaging attacks (like the flameskull’s fire ray) seem to be treated much like the “strongest natural attacks” above, but there aren’t many examples yet. Still, that guideline may work for now. Dragon breath weapons are upgraded much more than that, but until we have more dragons, I’m reluctant to recommend any guidelines there.
Saving Throws for Actions
5E saving throws are very different from 2E. They should probably be converted as follows:
2E Saving Throw 5E Saving Throw
Paralyzation, Poison, or Death Magic Constitution Rod, Staff, or Wand Wisdom (or Dexterity) Petrification or Polymorph Constitution (or Wisdom) Breath Weapon Constitution (or Dexterity) Spell Wisdom
Feel free to substitute a different ability score for the save, if it seems more appropriate.
You will need to calculate a Difficulty Class (DC) for the save your creature inflicts. The usual way to calculate this is 8 + proficiency bonus + the ability bonus of the creature for the relevant save. For example, a CR 2 creature with Constitution 13 (+1 bonus) that inflicts a Constitution save effect should require a DC of 11 (8+2+1).
The wraith’s Life Drain should be used in place of 2E’s energy drain attack.
Recharge
Some actions also have a recharge. Two examples are the giant spider’s Web and the young green dragon’s Poison Breath, which both have a recharge of 5-6.
Recharge seems to cover strong effects that, in 2E, could only be used a limited number of times per day, or required a number of rounds between uses.
My recommendation is to use “Recharge 5-6” for most limited-use actions, and keep “X per day” for especially strong attacks that should only be used once in a battle.
Actions without an Attack Roll
Many 5E creatures - such as the doppelganger, flameskull, grick, nothic, owlbear, and young green dragon - have Multiattack, allowing them to take more than one action per turn. If your 2E monster could attack more than once, you should probably give them Multiattack in 5E. Note that most creatures can only make two attacks - the only exception is the young green dragon, which can make three.
There are also a few creatures that can take actions not requiring an attack roll or saving throw. If your monster could do this in 2E, you can probably use them as is in 5E.
Reactions
Anything that could be converted into an Action, but requires some sort of trigger, should be categorized as a Reaction. Otherwise, they should be converted like other Actions.
A list of the known Reactions in 5E can be found here.
Final Notes
Everything not mentioned above, like Morale, should probably be dropped in 5E. Of course, if you feel it’s very important to the creature’s concept, feel free to port it over anyway.
Appendix 1: CR Estimator
The below conversion follows a very broad comparison of the 5E CR and 2E XP Value for the same creatures in both editions. It’s not perfect, but it works as a rough starting point.
5E CR 2E XP
0 7 ⅛ 15 to 35 ¼ 65 to 120 ½ 175 to 270 1 420 2 650 3 975 to 1400 4 2000 5 3000 to 4000 6 5000 to 6000 7 7000 8 8000 +1 +1000
Appendix 2: 1E
While there were several underlying changes between 1E and 2E, the monster statistics can be converted more or less the same as 2E creatures. There are a few differences, however, which are mostly cosmetic.
Movement rates are the same as 2E, but they are usually displayed in the following format:
[normal]”
/[flying]”
*//[swimming]” *
([burrowing]”)
*[web]”
@[climb]”
1E only recognizes three size categories: S (small), M (human-sized), and L (large). “M” is defined as 5-7 feet; “S” is anything smaller than 5 feet; “L” is anything larger than 7 feet. If a specific size in feet is given, you may use that number with the 2E size conversion; if not, you will have to choose an appropriate size yourself, based on the creature’s description.
XP Value is calculated differently from 2E. As such, if you want to use their XP Value to determine their 5E CR, you cannot use Appendix 1’s CR Estimator. Instead, use the following alternative table (ignoring the extra XP per monster hp):
5E CR 1E Basic XP Value
0 5 or less ⅛ 5 to 20 ¼ 20 to 50 ½ 50 to 100 1 100 to 200 2 200 to 350 3 350 to 650 4 650 to 900 5 900 to 1300 6 1300 to 1700 7 1700 to 2100 8 2100 to 2500 9 2500 to 3000 10 3000 to 3500 11 3500 to 4000 12 4000 to 4500 13 4500 to 5000 14 5000 to 5500 15 5500 to 6000 16 6000 to 6500 17 6500 to 7000 18 7000 to 7500 19 7500 to 8000 20 8000 to 9000 21 9000 to 10,000 22 10,000 to 15,000 23 15,000 to 20,000 +1 +5000
(Note that the original 1E Monster Manual does not provide XP Values at all; you have to refer to the 1E Dungeon Masters Guide.)
Psionic Ability is listed for many 1E monsters (as well as a smaller number of 2E monsters). Psionics rules are beyond the scope of this conversion, but you may wish to import any described psionic powers as Innate Spellcasting (see the Mind Flayer for an example), or as other traits, actions, or reactions as appropriate.
FYI, the 1E Monster Manual II has a list converting the damage ranges (2-8, etc.) to dice rolls, which may come in handy for both 1E and 2E conversions.