Hello modders, it's update time again, so to try and help everyone out I'll try to post a list of all modding related changes in the new 1.8 patch.
Structural Changes (requires updating existing files)
Stars: Now have a dlcID line like planets, above the abilities section. As before, "dlcID 204880" is used for items that do not originate from a DLC.
Player Entities: New line "GameEventSound:RandomEventDetected", located above "GameEventSound:CannonUnderConstruction". This will cause the game to crash if you do not add this line. It seems all three races use the same sound effect, so adding GameEventSound:RandomEventDetected "Effect_RandomEventDetected" for all races should suffice.
GalaxyScenarioDef & non-random Galaxy maps: The "player" section at the bottom of both of these file types has a new line that should be added "isMadVasariPlayer" below the line "isOccupationPlayer" Naturally this should be false for all pre-existing players, though if you want the new random events to work in your mod you should copy the MadVasari player to your GalaxyScenarioDef file.
player
designName "MadVasari"
inGameName "IDSScenarioPlayerNameMadVasari"
overrideRaceName "PhaseLoyalist"
teamIndex -1
startingCredits 0
startingMetal 0
startingCrystal 0
isNormalPlayer FALSE
isRaidingPlayer FALSE
isInsurgentPlayer FALSE
isOccupationPlayer FALSE
isMadVasariPlayer TRUE
themeGroup "PlayerPhase"
themeIndex 15
pictureGroup "PlayerPhase"
pictureIndex 15
If you want the new planet and star types to appear you'll of course need to add them to the GSD as well.
SkyBoxProperties.skyboxbackdropdata
New "environmentIlluminationMapName" line right below each "environmentMapName" line. It expects a texture reference, most of the vanilla ones are named things like "skybox02irradiance.dds". Probably has something to do with either the new shaders or stars, may cause a crash if you don't add these lines.
New Syntax (New modifiers we can use)
buffInstantActionType
- "ClearRecordedDamage" - Not yet sure what this does.
- "ChangePlayerIndexToNeutral" - Apparently we can now have proper neutral objects!
buffEntityModifierType
- "EnemyCultureSpread" - I guess this is like the CultureSpread one but only effects enemy culture.
targetFilter
- "EnvoyFrigate" - We can now specifically target envoy frigates.
RandomEventDefs.randomeventdefs
- New file used to define random events.
New/Modified Files List
All courtesy of ZombiesRus5. See his post and be generous with Karma. 
