To appease Khorne to approach the Brass Citadel in The Blood God’s Domain in Total War: Warhammer 3 you will need to fight in the Blood God’s Domain and build up 500,000 bloodshed points. This can be done in 2 ways:
Fight the armies that are scattered throughout the Blood God’s Domain or
Fight any armies in the Blood God’s Domain from rival factions.
I found that it took fighting about 5-6 of the armies until I had built enough bloodshed. You will then be able to approach the Brass Citadel to complete the quest battle. I found the best way to be able to keep fighting was to encamp and slowly move towards the various armies in the Blood God’s Domain who will come and attack you if you are close enough. The encamp stand allows you to replenish and I also usually picked the replenish option after winning fights.
To find a way through the maze to reach the Impossible Fortress in The Realm of the Sorcerer in Total War: Warhammer 3 you will need to use the Teleport Locus Points to gradually make your way along the islands.
The way to identify the right teleport locus points to go through, you will want to uncover Sigils. Every pair of teleport locus points will share the same sigil, so if you enter a teleport locus point with a given sigil you will arrive at the other teleport locus point with the same sigil. Sigils can be uncovered in 2 ways:
By defeating the armies on the islands and picking the option to reveal a sigil after you win and
By going to the strange places and picking the option to reveal a sigil.
Each faction in the Sorcerer’s Realm has their own unique path, the teleport locus points will lead them to different locations that they will for you so don’t expect to reach the same island if you follow another faction’s army.
The way I reached the Impossible Fortress is by using the encamp stance and gradually moving through each of the islands. The various armies on the islands threw themselves at me and I kept picking sigils until I found a way to the Impossible Fortress. The encampment stance meant that my troops were being replenished at approximately the rate I was losing them in battle. Entering a teleport locus points or a strange place will use up all of your movement.
There you have it. You will want to reveal sigils and then identify a path to the Impossible Fortress by going through the teleport locus points with matching sigils.