At the very top of the worldbuilder file, there is a section that specifies the options for that game. Here's an example from one of my files:
Code:
BeginGame
Era=ERA_ANCIENT
Speed=GAMESPEED_QUICK
Calendar=CALENDAR_DEFAULT
Option=GAMEOPTION_AI_NO_BUILDING_PREREQS
Option=GAMEOPTION_AI_NO_MINIMUM_LEVEL
Option=GAMEOPTION_NO_TECH_TRADING
Option=GAMEOPTION_NO_VASSAL_STATES
Option=GAMEOPTION_NO_GOODY_HUTS
Option=GAMEOPTION_NO_ESPIONAGE
Option=GAMEOPTION_DOUBLE_BONUSES
Option=GAMEOPTION_DOUBLE_EVENTS
Option=GAMEOPTION_NO_GLOBAL_COUNTER
Option=GAMEOPTION_NO_HYBOREM_OR_BASIUM
Option=GAMEOPTION_NO_LAIRS
Option=GAMEOPTION_NO_UNIQUE_IMPROVEMENTS
Option=GAMEOPTION_NO_ACHERON
Option=GAMEOPTION_NO_ORTHUS
Victory=VICTORY_TIME
Victory=VICTORY_CONQUEST
Victory=VICTORY_DOMINATION
GameTurn=0
MaxTurns=480
MaxCityElimination=0
NumAdvancedStartPoints=482
TargetScore=0
StartYear=0
Description=
ModPath=
EndGame
If you want Orthus and Acheron, make sure the NO_ORTHUS and NO_ACHERON lines *aren't* in your worldbuilder file. The NO_GLOBAL_COUNTER line will inhibit the Horsemen; NO_HYBOREM_OR_BASIUM means Hyborem and Basium can't be summoned.