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Murranji's Great Bastion Expansion Mod

The key goal of the mod is to turn the Great Bastion feature into a more engaging and interactive mechanic by increasing the variety of enemies that can attack the Bastion and adding unique and specialised ways to bolster its defences to enable closely fought giant siege battles.

The addition of a new pool of powerful mercenaries that is earned through invasions and battles at the Great Bastion is intended to demonstrate a way that the mechanic could be turned from solely a one sided army spawner into something that can be turned into providing a reward for the other parts of the campaign.

The mod adds an additional faction effect for Miao Ying to unlock new unusual locations in the Great Bastion (IE only). It also enables and fully integrates this updated Great Bastion mechanic for Yuan Bo, who earns an extra turn reduction for his Stone and Steel token cooldown whenever he wins a battle in the Great Bastion provinces. For non Shadows of Change version see the no SoC submod. The key features of the mod are:


Increased Invader Variety:
Invasion forces can now spawn as any mono Chaos God as well as the Daemons of Chaos, the Chaos Dwarfs, Warriors of Chaos, and Norsca, all with full DLC rosters. All armies have randomised units and increase in strength over time.

Ongoing Invasions
While an Invasion is ongoing the invaders will spawn additional reinforcement forces every 4 turns. Reinforcements are not necessarily the same race that attacks at the start of the invasion. Destroy all invaders once and for all to end the invasion.

Random Assaults
Other races bent on destruction will now launch surprise attacks on the Great Bastion. Fend off the Beastmen, Greenskins, Skaven, Ogres, Dark Elves, Lizardmen and Cathayan Rebels when they threaten your or your allies gates. Random assaults won’t occur while an invasion is ongoing.

Dynamic Threat Meter
As the average level of Chaos corruption across your provinces rises the constant threat meter will also increase - from the flat 6 to up to 10%. Control the corruption across your provinces to slow the growth of the threat meter.

Fixed bugs that were reducing the number of invasion forces
The vanilla version of the Great Bastion mechanic includes 2 bugs which could reduce the number of Invasion armies spawned by up to 2 forces per invasion. This mod fixes those parts of the script ensuring the full number are spawned.

Oh and Zhatan will no longer destroy the invasion faction all by himself for you any more…

All 4 building chains in the Defence super chain have been upgraded to provide an additional powerful defensive buff or reward.

Sanctum chain - automatically summon an emergency force of reinforcements whenever a Gate settlement is besieged. The force grows in strength as you level up the building.

Fortification chain - unlocks a unique and powerful ancillary and banner for each level of the chain, with different ancillaries across the 3 gates.

Artisan chain - provides an additional specialised buff to the forces of Yin garrisoned in a gate region to help you rain death on approaching enemies.

Refectory chain - provides access to the ‘Great Bastion Veterans’, an additional mercenary unit variant of several Cathayan units with access to a unique ability that increases their melee attack and defence when they are docked on a wall or a hard point. Increase your chances of recruiting these mercenaries by levelling up the building.

As castellan of the Great Bastion Miao Ying has an additional faction effect that gives her a chance of spawning new unusual locations only available in the Great Bastion provinces. These buildings provide additional garrison troops and unique faction bonuses. This works for the AI too.

The dual cities of Wei-Jin and Nan-Gau stand ready to aid in the defence of Cathay. While these cities are held in any Cathayan faction’s hands they will each provide a random buff every turn to the Yang and Yin units in the Great Bastion garrisons. However if a city falls then the buff they provide to the Great Bastion will fail also.

If your allies have a Sanctum building they will summon you an emergency force to help defend their settlement as well. At the start of the game you will get the option to automatically declare war on any faction that attacks a gate settlement.

Sick of the Imperial Wardens failing their one job? Now you can help them out directly instead. Prefer the challenge of fighting off Chaos forces and Sniktch and Lokhir Felheart at the same time - just leave them to fight alone.

Builds in the popular requirement to disable siege attrition to any garrisoned forces.

If you prefer to take a break from the waves of invasions capture the 7 regions closest to the Great Bastion (Bloodwind Keep to the Stonesky Foothills on Immortal Empires and Red Wastes to Eastern Steppes on Realm of Chaos). This will keep the threat meter at 0. If you ever want to start the invasions up again just abandon one of those settlements and the threat meter will begin to increase.

And more…

Compatibility
This will overwrite any changes made by mods that modifies the wh3_campaign_great_bastion.lua script.
Works for Immortal Empires, Immortal Empires Expanded and Realm of Chaos.
SFO submod - for veterans units

Chinese translation/中文翻译

FAQ:
How many armies spawn with the mod?

Army spawn is set as a default 3/4/5/6 based on turn length 1/25/50/75
Playing on hard will spawn an additional army from turn 1
Playing on very hard or legendary will spawn 2-3 extra armies for 5/6/7/9 total for all turns.

This is too hard!? / This is too easy!?

The goal was to make the invasions return to the earlier iteration of the mechanic where up to 8 armies would assault the gate in the late game, while giving players extra tools to handle it. Extra difficulty is intended to be provided for very hard/legendary difficulty through extra spawns while keeping the number of spawns lower for normal.

That said I am interested in hearing if there are thoughts on balancing in the comments - are the invasions or the dilemma battles too hard or too easy, too common or not enough?

Where are Great Bastion Veterans recruited?

They are recruited from the Regiments of Renown faction mercenary pool.

How does the mechanic work for Yuan Bo?

It works the same as for Miao Ying and Zhao Ming. For Yuan Bo it is more worthwhile to fight battles as it will decrease his pending token cooldown by an extra turn.

Is Shadows of Change required?

Yes

Bugs:
Known potential bugs are below. Please list any other unexpected bugs you encounter in the comments.

In some circumstances spawned armies won’t properly despawn after a battle. This normally occurs if the leading general dies but the force survives. If you have an emergency force that doesn’t despawn I recommend disbanding it.

On occasion armies may improperly spawn for invasion forces, if an invasion is launched without the armies on the map the invasion will immediately end.

Spawned generals can earn traits when they defeat legendary lords and the event feed won’t be suppressed.

Credits:
Scripting and db work - Murranji (with assistance from ChatGPT 4o).
Based on vanilla work by CA
Thanks to RPFM