We successfully completed the prolog after 8 sessions and everyone had a good time. The players got into their characters and we are already beginning to see some interparty disagreements which are going to be fun to explore as we begin the campaign. The prolog was a good short adventure for the group to begin developing their characters and relationships with each other.
As for the prolog itself, I found that placing it in the empire was a good choice as it gave credibility to the fact that the players would all have been hired to come there. Many elements of the prolog have to be rewritten to fit into the empire and into the Warhammer universe, as there are many elements that are distinctly Spanish. I would properly consider placing it in Tilea if I were to run it again just to make it more exotic. This would require more in terms of validating why the characters would travel there for the quest but it would be an interesting setting to explore.
The Kharisiri are very good adversaries for Warhammer with a nice touch of horror, but a Gm running the campaign prolog needs to think about what will happen when the witch hunters become involved and how to keep the player invested in going ahead with the Journey. Several of my players didn't trust that the witch hunters would return the ward to the temple so they persuaded the more religious characters to leave the order of the burning touch out of their mission. But I can definitely see issues if the GM isn't prepared to help the players stay focused on the quest. I found it was easy to convert the traveling distances to fit with Warhammer and find ways for them to travel by boat or mules. I used Augustus to pay for the expenses and the players got a sense of him as a ham of many funds.
My players spent a lot of time in Meissen which was great fun but also caused the prolog to be prolonged quite a bit. As a GM it's important to plan out how to get the players out of the starting location and onward on the path to the temple otherwise its quite possible to get mixed up in the intrigues of the city. This might be fine for the group but in any case, I recommend having a plan ready.
I changed Naira to be a local witch who had advice and premonitions to offer the players as this gave me a chance to introduce the players to the mystics of Warhammer and pair Mira with an alternate path for her character. I found that the village as its portrayed in the original campaign fits very well with Warhammer and the horror aspect of the Kharisiri, but our group had confronted Augustus before coming to the village and therefore I removed some of the horror aspects since we were keen on getting to the temple. I am sure another GM could run an excellent horror session in the village should it make sense for their party.
I hardly changed anything around the temple itself, it is an excellent location which fits perfectly into Warhammer and it was easy to get the players both anxious about what they would find and very cautious about how to proceed. We had a blast exploring the site and Otto almost scored a corruption point as he tried to investigate the top of the pyramid.
In general, I found that it was a good introduction even if it does require some imaginative storytelling to explain why the players have all joined such an expedition. There are many possibilities for the players to interact and build a relationship with Reingard, which we will need to start the campaign. Though the prolog doesn't build much in terms of content which can be used in the following campaign it builds a lot of relationships between the characters which can be built upon in the campaign. We could easily have spent much more time in the prolog and if we weren't eager to get started on the campaign I would properly have spent more time diving into the horror and history of the Kharisiri and Augustus' background. I feel that there's a missed opportunity there to explore and maybe play more into the horror which is Augustus' life, and how he ended up in that situation.
I have added the list of NPC stats I used during the prolog. Not all of them came into effect and play but it was good to have them.