D20 to d20 Conversion Rules

May need some tinkering by your GM!

The game systems in d20 are based on the popular d20 System. However, there are a number of important differences, notably in how d20 handles damage and injury. This appendix offers conversion guidelines for players familiar with other d20 System games and products who are interested in adapting those materials for use with d20. Among other things, this opens up a wide range of source material usable in your d20 game, including various creatures, supporting characters, supplemental rules, and so forth. It also allows you to adapt material from d20 to your favorite d20 System games as well.

Abilities

Other d20 games rate ability scores on a scale from 1 to 20 or more, with ability modifiers based on the ability score. Those modifiers are equivalent to the –5 to +5 or more scores found in d20. When using other d20 creatures in d20, drop the ability scores and just use the ability modifiers. When converting d20 creatures for use in other d20 games, determine ability scores by doubling the d20 ability modifier and adding 10. Treat a result of 0 as 1. So Strength +1 becomes Strength 12 (1 x 2 + 10), while Intelligence –5 becomes 1 (–5 x 2 + 10 = 0, which becomes 1).

Damage and Injury

Damage in most d20 System games is recorded using hit points. Essentially, each character and creature has a number of hit points based on their level (modified by things like Constitution), and each attack inflicts a number of hit points of damage. When hit points drop to a certain level, certain conditions, like disabled and dying, come into play.

The d20 system of damage involves a Toughness saving throw in place of hit points, with damage conditions showing the effects of damage. When converting a d20 character to d20, give the character a Toughness bonus based on Constitution, with any appropriate modifiers for the Defensive Roll and Tough feats.

Toughness and Hit Points

Damage Reduction: A creature with damage reduction receives +2 to its Toughness save bonus for every 5 points of damage reduction. This bonus does not apply against damage from sources that bypass the damage reduction. For instance, a werewolf does not gain a Toughness bonus from damage reduction for damage inflicted by silver weapons.

Energy Resistance: A creature receives +2 to its Toughness bonus for every 5 points of energy resistance it possesses, but only against energy attacks of the matching type.

Toughness feat: A character receives a cumulative +1 to his Toughness bonus every time he takes the Toughness feat, the equivalent of the Tough feat in d20. When converting d20 characters with Tough to hit points, the Tough feat grants 3 additional hit points on top of the character’s total (based on level and Constitution).

Damage Bonus

In d20, attacks have a damage bonus, used to determine the Difficulty of the target’s Toughness save. In d20, attacks have a damage roll, a die roll plus a modifier determining how many hit points the attack removes from the target.

To quickly convert d20 damage bonus to dice of damage, divide the base damage bonus (not including modifiers for abilities like Strength) by 2; the attack does that many d6 of damage. If there’s a remainder left over, the attack does an additional d4 damage. Add the attacker’s Strength modifier to the total damage, so Strength 18 adds +4 damage to the attack’s total damage, after it is rolled.

Damage Dice to Damage Bonus
Die Type	Base Damage Bonus
1d3 or lower	+0
1d4	+1
1d6	+2
1d8	+3
1d10	+4
1d12	+5

To convert d20 damage to d20 damage bonus, see the Damage Dice to Damage Bonus table. If an attack does multiple dice of damage, multiply the damage bonus on the table by the number of dice rolled. The exception to this rule is for attacks based on a d3 or d2, since multiplying by zero gives a result of zero; in this case, every additional die adds +1 to the bonus (so an attack of 4d3 has a bonus of +3).

To this base damage bonus, add any damage bonuses for Strength, magical enhancement, special abilities, and the like, as normal. If an attack includes bonus damage dice, such as a rogue’s sneak attack bonus or energy damage from a magical weapon, convert that damage to a bonus as above and add it to the attack’s base damage.

In some circumstances, attacks may do a bit more or less damage than normal. A critical hit does more damage than usual, while many attack spells do only half damage if the target succeeds in a saving throw. Magical Healing

Instead of healing a certain number of hit points, d20 System healing spells in d20 grant a magical recovery check, using the normal Difficulty. The character using the healing magic makes the recovery check for the wounded subject, as follows:

d20 + caster level + magic bonus The magic bonus depends on the spell used; see the Spell Changes section later in this appendix.

The recipient heals the most serious wound condition if the magical recovery check succeeds. Every 10 points by which the magical recovery check result succeeds, the recipient’s next most serious damage condition heals. (Unlike natural healing or the Cure power, magical healing can heal multiple damage conditions at once.) If an attempt to use magical healing on a dying character fails, the recipient of the spell still stabilizes automatically.

Supernatural Healing

The paladin’s lay on hands ability, the monk’s wholeness of body ability, and other such supernatural healing powers allow characters to make one or more magical recovery checks per day. The total hit points the character can heal per day using the standard d20 System rules becomes a bonus to his magical recovery check. The character decides how much, from a minimum of +1 to the full bonus, to allocate to any given magical recovery check. Once the total bonus is used up, the character can make no more supernatural healing checks that day. This otherwise works the same way as a healing spell and can improve damage conditions by multiple steps.

Damage to Objects

Just as d20 characters and creatures suffer damage conditions instead of losing hit points, so too do inanimate objects. The effects of damage are slightly different, since objects don’t feel pain or suffer from wound trauma, but the core system remains the same.

Toughness and Hit Points for Objects

In d20, each object has a Toughness bonus. In d20, objects have two qualities: hardness and hit points. Hardness serves as damage reduction; the object ignores points of damage equal to its hardness each round. Hit points work like those of creatures, except objects are destroyed at 0 hit points instead of being disabled.

To convert from d20 Toughness to d20, give the object hardness equal to its d20 Toughness and hit points equal to 2.5 times its d20 Toughness (rounding down).

To convert from d20 hardness and hit points to d20 Toughness, give an object +1 Toughness for every 5 hit points and +2 Toughness for every 5 points of hardness.

Example: A strong wooden door has hardness 5 (+2) and 20 hp (+4), giving it a total +6 Toughness bonus in d20. A stone door has hardness 8 (+3) and 60 hit points (+12) for a total +15 Toughness bonus.

Feat Changes

The d20 System metamagic feats Empower Spell and Maximize Spell must be changed in d20 to reflect the nonvariable nature of damage and healing spells. Empower Spell increases the bonus of such spells by 50 percent (round down). Maximize Spell doubles the bonus of suitable spells. If a spell is both empowered and maximized, its bonus increases by 150 percent. All other aspects of the feats remain the same.

Example: An explosive runes spell inflicts 6d6 damage in d20, which translates to a +12 damage bonus. An empowered explosive runes has a +18 damage bonus (+12 x 1.5); a maximized explosive runes has a +24 damage bonus (+12 x 2); and an empowered, maximized explosive runes has a +30 damage bonus (+12 x 2.5).

Spell Changes

The following d20 spells have altered effects or mechanics in d20 to reflect the nature of the damage system.

• Cure Critical Wounds: This spell provides a base +12 bonus to the magical recovery check, with an additional +1 bonus per caster level (to a maximum +20 caster level bonus).

• Cure Light Wounds: This spell provides a base +3 bonus to the magical recovery check, with an additional +1 bonus per caster level (to a maximum +5 caster level bonus).

• Cure Minor Wounds: This spell provides a +0 bonus to the magical recovery check, with no caster level bonus.

• Cure Moderate Wounds: This spell provides a base +6 bonus to the magical recovery check, with an additional +1 bonus per caster level (to a maximum +10 caster level bonus).

• Cure Serious Wounds: This spell provides a base +9 bonus to the magical recovery check, with an additional +1 bonus per caster level (to a maximum +15 caster level bonus).

• Cure, Mass: All cure spells (except for cure minor wounds) have corresponding mass cure versions. Each provides the same bonus to the magical recovery check as the single target version, but the maximum caster level bonus increases by +20. Mass cure moderate wounds, for example, provides a base +6 bonus with a maximum +30 caster level bonus.

• Harm: This spell inflicts damage on the target, with a base +10 damage bonus, and an additional +2 damage bonus per caster level (to a maximum +30 caster level bonus). The total damage bonus is halved if the target makes a successful Will save, and the spell cannot reduce the target past disabled.

• Heal: This spell provides a base +10 bonus to the magical recovery check, with an additional +2 bonus per caster level (to a maximum +30 caster level bonus). All other factors of the spell function as described in the Player’s Handbook.

• Regenerate: In addition to regenerating the subject’s body parts, this spell provides a base +12 bonus to the recovery check, with an additional +1 per caster level (to a maximum +35 caster level bonus). Spells inflicting hit point damage (other than harm) should be adjusted as shown on the Damage Dice to Damage Bonus table.

Converting Creatures

Converting d20 System creatures for use with d20 is a simple process:

1. Use the creature’s Constitution and Size to determine its Toughness. 2. Convert hit point damage of the creature’s attacks to a damage bonus.

3. Convert any spell-like abilities into equivalent powers.

4. Convert any d20 System skills to d20 skills. Generally, this means combining skills like Listen and Spot or Hide and Move Silently, using the average of the skill bonuses.

Most other creature statistics remain the same between the two systems, so it’s fairly easy to use creatures from any d20 System book in d20.