system-comparison

name	system-comparison
description	Compare D35E (legacy Foundry system), dnd5e, and PF2e implementations side-by-side. Use when deciding data structure for a new item type, comparing buff/AE/RuleElement approaches, checking HP/saves/BAB/AC paths across systems, reviewing condition implementations, or understanding why dnd35e chose a particular design over the D35E approach.

System Comparison Skill

When to Use This Skill

Ask questions like:

• "How does D35E store buffs compared to dnd5e?"
• "How do the three systems handle item Active Effects?"
• "What does D35E's changes template look like vs dnd5e AEs?"
• "How do the three Foundry systems structure actor HP?"
• "How does PF2e handle conditions compared to D35E?"

This skill helps you:

• Compare Foundry system implementations across D35E (legacy), dnd5e, and PF2e
• Understand migration targets — what D35E did and how dnd35e (our new system) improves on it
• Port mechanics between Foundry system paradigms
• Identify D35E patterns that carry over or need redesign
• Plan compatibility with world data from the old D35E system

Terminology

• D35E = the legacy Foundry VTT system (system ID D35E, last known version ~2.4.3) we are rebuilding from
• dnd5e = the official Foundry D&D 5e system by Atropos et al.
• PF2e = the official Foundry Pathfinder 2e system
• dnd35e = our new system (what we are building)

For raw 3.5e rule lookups use /srd-lookup. For detailed D35E schema reference use /d35e-reference.

Actor Data Comparison

Hit Points

Field	D35E	dnd5e	PF2e
Current HP	system.attributes.hp.value	system.attributes.hp.value	system.attributes.hp.value
Max HP	system.attributes.hp.max	system.attributes.hp.max	system.attributes.hp.max
Temp HP	system.attributes.hp.temp	system.attributes.hp.temp	system.attributes.hp.temp
Non-lethal	system.attributes.hp.nonlethal	❌ not a field	❌ not a concept
Wound threshold	❌	❌	system.attributes.hp.sp (stamina)

D35E uses non-lethal damage as a separate tracked value. PF2e uses a stamina system at GM option. dnd5e has no non-lethal concept.

Ability Scores

Field	D35E	dnd5e	PF2e
Score	system.abilities.str.value	system.abilities.str.value	system.abilities.str.mod (derived)
Modifier	system.abilities.str.mod (derived)	system.abilities.str.mod (derived)	Proficiency-based, no raw score
Temp score	system.abilities.str.total, system.abilities.str.userPenalty	❌	❌
Damage/drain	system.abilities.str.damage, system.abilities.str.drain	❌	system.abilities.str.apex for item bonus

Key difference: D35E tracks ability damage/drain as permanent vs temporary reduction. PF2e has no ability score concept — everything is proficiency + item bonus.

Saving Throws

Throw	D35E path	dnd5e path	PF2e path
Fortitude/Con	system.attributes.savingThrows.fort	system.abilities.con.save	system.saves.fortitude
Reflex/Dex	system.attributes.savingThrows.ref	system.abilities.dex.save	system.saves.reflex
Will/Wis	system.attributes.savingThrows.will	system.abilities.wis.save	system.saves.will

D35E stores saves as { base, ability, misc, total }. dnd5e stores a save modifier per ability. PF2e stores a proficiency rank.

Attack (BAB)

Component	D35E	dnd5e	PF2e
Base attack	system.attributes.bab.total	❌ (no BAB)	❌ (proficiency rank instead)
Attack bonus	BAB + STR/DEX + changes	Proficiency + STR/DEX	Proficiency rank + STR/DEX
Full attack	Iteratives from BAB ≥ 6	Extra Attack class feature	MAP (multiple attack penalty)

D35E uses BAB stored directly on the actor (aggregated from class items). dnd5e only uses proficiency. PF2e uses proficiency ranks (untrained/trained/expert/master/legendary) and the MAP system.

---

Item Type Comparison

Weapons

Feature	D35E	dnd5e	PF2e
Item type	weapon	weapon	weapon
Damage formula	system.damage.parts[] (array of [formula, type])	system.damage.parts[]	system.damage.dice + system.damage.die
Critical threat	system.ability.critRange	system.critical.threshold	system.criticalHit
Critical multiplier	system.ability.critMult	❌ (always ×2)	❌ (crit is double dice)
Attack bonus	changes[] targeting ~attack	system.attackBonus	system.bonus.value
Weapon groups	❌	system.weaponType	system.group

Armor / Equipment

Feature	D35E	dnd5e	PF2e
Item type	equipment	equipment	armor
AC bonus	system.armor.value	system.armor.value	system.acBonus
Max Dex	system.armor.dex	system.armor.dex	system.dexCap
Check penalty	system.armor.acp	system.armor.checkPenalty	system.checkPenalty
Equip slot	system.slot (head/body/etc)	system.armor.type	system.category + traits

Buffs

Feature	D35E	dnd5e	PF2e
Implementation	Item type buff on actor	Active Effect on actor	Item type effect on actor
Toggle on/off	system.active boolean	AE enable/disable	system.active boolean
Duration	system.duration object	AE duration	system.duration
Applies to	system.changes[] → actor stats	AE changes[]	system.rules[] (RuleElements)
Stacking	Manual modifier field, no enforcement	No stacking rules	PF2e enforces type stacking

D35E buffs are items. dnd5e uses pure AEs. PF2e uses effect items with RuleElements.

Spells

Feature	D35E	dnd5e	PF2e
Item type	spell	spell	spell
Spell level	system.level	system.level	system.level.value
Prepared	system.preparation.preparedAmount	system.preparation.mode	system.location (spellbook)
School	system.school	system.school	system.traits.value[]
Components	system.components	system.components	system.components.value[]
Buff creation	Creates buff item on target	Creates AE on target	Creates effect item on target

Feats

Feature	D35E	dnd5e	PF2e
Item type	feat	feat	feat
Feat type	system.featType (feat/classFeat/etc)	system.type.value	system.category
Prerequisites	system.prerequisites.value[]	None enforced	system.prerequisites.value[]
Uses	system.uses	system.uses	system.frequency
Passive changes	system.changes[]	Creates AE	system.rules[] (RuleElements)

---

Active Effects / Changes Comparison

This is the most significant architectural difference between the three systems.

D35E changes Template

D35E does NOT use Foundry Active Effects for stat modification. Instead items carry a changes array:

{
  "system": {
    "changes": [
      { "formula": "2", "operator": "+", "target": "~acBonus", "modifier": "armor", "priority": 200 },
      { "formula": "1", "operator": "+", "target": "~bab",      "modifier": "enhancement", "priority": 0 }
    ]
  }
}

Field	Meaning
formula	Value formula (string, may be an expression)
operator	+, -, = (add/subtract/set)
target	Stat path using ~ shorthand (e.g. ~acBonus, ~bab, ~str)
modifier	Bonus type label (not enforced for stacking)
priority	Application order (higher = later)

Stacking is not enforced in D35E — all changes are summed. The GM/system designer manually structures items to avoid stacking.

dnd5e Active Effects

dnd5e uses Foundry's native AE system:

{
  "changes": [
    { "key": "system.defense.normal", "mode": 2, "value": "2", "priority": 20 }
  ]
}

mode values: 0=Custom, 1=Multiply, 2=Add, 3=Downgrade, 4=Upgrade, 5=Override

No bonus type stacking enforcement. Advantage/disadvantage handled separately from numeric bonuses.

PF2e Rule Elements

PF2e replaces AEs entirely with RuleElement objects:

{
  "system": {
    "rules": [
      { "key": "FlatModifier", "selector": "ac", "value": 2, "type": "armor" },
      { "key": "FlatModifier", "selector": "attack-roll", "value": 1, "type": "item" }
    ]
  }
}

PF2e fully enforces stacking — the type field is used to deduplicate (only highest of each type applies). Conditions are first-class items, not flags.

---

Condition Comparison

Condition	D35E implementation	dnd5e implementation	PF2e implementation
Stunned	ActiveEffect flag or changes[]	AE with statuses	effect item type condition
Frightened	system.attributes.conditions.frightened	AE statuses	effect with system.value (severity)
Prone	ActiveEffect or system.conditions	AE statuses	condition item, applies MAP +2
Invisible	ActiveEffect	AE statuses	condition item, RuleElements handle effects
Grappled	system.attributes.conditions.grapple	AE statuses	condition item

Key difference: PF2e conditions are first-class items that carry their own RuleElements. D35E and dnd5e use flags/AEs, requiring the system to hard-code condition effects.

---

Feat/Skill Comparison

Skills Storage

Field	D35E	dnd5e	PF2e
Skill ranks	system.skills.per.rank	❌ (no ranks)	❌ (proficiency rank)
Class skill	system.skills.per.cs (boolean)	❌	❌
Modifier	system.skills.per.mod	system.skills.per.total	system.skills.per.value (proficiency)
Synergy	system.skills.per.synergy bonus via changes[]	❌	❌
Total	system.skills.per.total	system.skills.per.total	Computed from proficiency + ability

D35E has 40+ individual skills; dnd5e has 18; PF2e has 16 core + lore skills.

---

Compendium Structure Comparison

Pack type	D35E	dnd5e	PF2e
Spells	dnd35e.spells	dnd5e.spells	pf2e.spells
Feats	dnd35e.feats	dnd5e.feats	pf2e.feats
Conditions	(Not Implemented AE yet)	dnd5e.rules	pf2e.conditionitems
Monsters	dnd35e.monsters	dnd5e.monsters	pf2e.monstercore
Classes	dnd35e.classes	dnd5e.classes	pf2e.classes

---

When to Use This Comparison

Use this skill when:

• Implementing a mechanic and need to see how other Foundry systems approached it
• Deciding data structure for a new item type or field
• Reviewing how D35E stored something before designing dnd35e's version
• Checking if a pattern from dnd5e or PF2e applies to our 3.5e rebuild

Use /d35e-reference instead when:

• You need exact D35E schema field names, paths, and types
• You are writing a migration script mapping old fields to new ones
• You need to understand D35E item/actor templates in detail

Use /srd-lookup instead when:

• You need to look up raw 3.5e rules (how many attacks at BAB +11, etc.)
• You want the official SRD text for a mechanic, spell, or condition

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Gotchas

• D35E changes[] stacking is NOT enforced — every entry is summed regardless of modifier type. PF2e RuleElements actually deduplicate by type; D35E and dnd5e do not. Comparison tables showing the same field name across systems do not imply the same stacking behavior.

• PF2e has no ability scores, only modifiers — there is no str.value (a score like 18) in PF2e; everything works from the +4 modifier. Never look for a score field in PF2e schema.

• dnd5e has no BAB concept — the field does not exist. All attack math is proficiency bonus + ability modifier. Do not assume any D35E bab path maps to a dnd5e equivalent.

• D35E buffs are Item documents, not AEs — they are Items of type buff with system.active. dnd5e uses pure AEs on the actor; PF2e uses effect items with RuleElements. These are architecturally different despite surface similarity.

• System IDs are case-sensitive: D35E, dnd5e, pf2e — wrong case causes silent filtering failures in Foundry pack and world lookups.

Related Skills

• /d35e-reference: Detailed old D35E schema field reference for migration
• /srd-lookup: Raw 3.5e SRD rules lookup (online + local journal)
• /foundry-reference: Foundry VTT v14 API for implementing mechanics in code
• /implementation-guide: Step-by-step for adding a mechanic to dnd35e