Hello!
First of all, you need of course FinalBIG to open and change / create the correct files. When you got this, you can already start.
I would suggest to create your own .big-file, because otherwise you would overwrite the original data. Just in chase you did something wrong, so it doesn't destroy something.
Now you should search for the object DwarvenSummonedCitadelKe
ep, in Edain this is inside the .ini data\ini\object\goodfaction\structures\dwarven\dwarvensummonedcitadel.ini
There you should be able to e.g. add this entry
Behavior = TunnelContain ModuleTag_Contain
ObjectStatusOfContained = UNSELECTABLE ENCLOSED
ContainMax = 5
DamagePercentToUnits = 0%
PassengerFilter = ANY +INFANTRY +BANNER +CAVALRY -MONSTER -SUMMONED -COMBO_HORDE -DwarvenBattleWagon -DwarvenBattleWagon_Eisenberge
AllowEnemiesInside = No
AllowAlliesInside = No
AllowNeutralInside = No
AllowOwnPlayerInsideOverride = Yes
NumberOfExitPaths = 1 // Defaults to 1. Set 0 to not use ExitStart/ExitEnd, set higher than 1 to use ExitStart01-nn/ExitEnd01-nn
PassengerBonePrefix = PassengerBone:ARROW_ KindOf:INFANTRY
EntryPosition = X:0.0 Y:0.0 Z:0.0
EntryOffset = X:80.0 Y:0.0 Z:0.0
ExitOffset = X:100.0 Y:0.0 Z:0.0
EnterSound = RuinedTowerEnterSound
KillPassengersOnDeath = No
ShowPips = No
ExitDelay = 0
End
eventhough most offsets and positions are probably incorrect, because these belong to the mineshaft.
Also you probably have to add some entries in the CommandSet, otherwise the units shouldn't be able to exit.
And you probably have to remove this:
Behavior = HordeGarrisonContain ModuleTag_hordeGarrison
ObjectStatusOfContained = UNSELECTABLE CAN_ATTACK ENCLOSED
ContainMax = 2
DamagePercentToUnits = 0%
PassengerFilter = GENERIC_FACTION_GARRISONABLE
AllowEnemiesInside = No
NumberOfExitPaths = 1 // Defaults to 1. Set 0 to not use ExitStart/ExitEnd, set higher than 1 to use ExitStart01-nn/ExitEnd01-nn
EntryPosition = X:7.0 Y:-40.0 Z:0.0
EntryOffset = X:7.0 Y:-80.0 Z:0.0
ExitOffset = X:7.0 Y:-80.0 Z:0.0
EnterSound = RuinedTowerEnterSound
KillPassengersOnDeath = No
ShowPips = No
End
however this gives you the correct positions and offsets you need above.
Most of the time it's btw the best option to just search for something you know works the way you want something else to work (like the citadel to have a tunnel function) and use the working implementation as a help. Worst thing to happen is that the game crashes.
Greetings
Melkor Bauglir