It’s possible that you entered a city while being poisoned and the venom is strong enough to persist even after leaving this city. The game saves when entering a city, so this could result in your character dying every time when leaving the city. In this case, you should download a suitable savegame from our savegame database to continue the game.
We're currently working on a fix for this issue. In the meantime, you're still able to complete the last quest and the game properly by downloading the last savegame ("Chapter 5, Iram ") for your selected slot from our official savegame database.
You can also find a description about how to implement the savegame on the top of the savegame database page. Thank you for your understanding!