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EFF file format

Applies to:
BG1: TotS, BG2, BG2: ToB, IWD, IWD:HoW, IWD:TotL

General Description
This file format describes an effect (opcode) and its parameters. The format is an extended version of that found embedded in creatures, items and spells, and is a replacement for the version 1 embedded effects used in BG1.

EFF V2.0
Overall structure:
  • Header
  • Body

    • EFF V2.0 Header

    Offset Size (data type) Description
    0x0000 4 (char array) Signature ('EFF ')
    0x0004 4 (char array) Version ('V2.0')

    EFF V2.0 Body

    Offset Size (data type) Description
    0x0008 4 (char array) External EFFs - the field is the same as the signature field from the header
    Embedded EFFs - this field is zeroed out
    0x000c 4 (char array) External EFFs - the field is the same as the version field from the header
    Embedded EFFs - this field is zeroed out
    0x0010 4 (dword) Opcode number
    0x0014 4 (dword) Target type
    0x0018 4 (dword) Power
    0x001c 4 (dword) Parameter 1
    0x0020 4 (dword) Parameter 2
    0x0024 1 (char) Timing mode
    • 0=Duration
    • 1=Permanent
    • 2=While equipped
    • 3=Delayed Durationv
    • 4=Delayed
    • 5=Delayed (transforms to 8)
    • 6=Duration?
    • 7=Permanent?
    • 8=Permanent (unsaved)
    • 9=Permanent (after Death)
    • 10=Trigger
    0x0025 1 (char) Unknown
    0x0026 2 (word) Timing ?
    0x0028 4 (dword) Duration
    0x002c 2 (word) Probability 1
    0x002e 2 (word) Probability 2
    0x0030 8 (resref) Resource
    0x0038 4 (dword) Dice Thrown
    0x003c 4 (dword) Dice Sides
    0x0040 4 (dword) Saving throw type
    • bit 0: Spells
    • bit 1: Breath
    • bit 2: Death
    • bit 3: Wands
    • bit 4: Polymorph
    NB. If more than 1 saving throw type is specified, the target rolls against their best save
    0x0044 4 (dword) Save bonus
    0x0048 4 (dword) Variable ?
    0x004c 4 (dword) Primary type (school)
    0x0050 4 (dword) Unknown
    0x0054 4 (dword) Parent resource lowest affected level
    0x0058 4 (dword) Parent resource highest affected level
    0x005c 4 (dword) Resistance
    • 0=Nonmagical
    • 1=Dispel/Not Bypass
    • 2=Not Dispel/Not Bypass
    • 3=Dispel/Bypass
    0x0060 4 (dword) Parameter 3
    0x0064 4 (dword) Parameter 4
    0x0068 8 (bytes) Unknown
    0x0070 8 (resref) Parameter 5 (VVC)
    0x0078 4 (dword) Unknown
    0x007c 4 (dword) Unknown
    0x0080 8 (resref) Caster X coordinate
    0x0084 4 (dword) Caster Y coordinate
    0x0088 4 (dword) Target X coordinate
    0x008c 4 (dword) Target Y coordinate
    0x0090 4 (dword) Parent resource type (0=None, 1=Spell, 2=Item)
    0x0094 8 (resref) Parent resource
    0x009c 4 (dword) Parent resource flags (from SPL 0x18 or ITM ext header 0x26)
    0x00a0 4 (dword) Projectile
    0x00a4 4 (dword) Parent resource slot
    0x00a8 32 (bytes) Variable
    0x00c8 4 (dword) Caster level
    0x00cc 4 (dword) Unknown
    0x00d0 4 (dword) Secondary Type
    0x00d4 4*15 (dword) Unknown