Trial by Fire is a quest in The Witcher 2: Assassins of Kings. It is the fourth piece of "back-story" which Geralt recalls while Roche interrogates him.
As King Foltest, Geralt, Triss, and Roche get nearer to La Valette Castle's temple, they are attacked by a dragon.
Run to the left or right, into the nearest wooden 'bridge tunnel'. As long as the roof is not destroyed, you are safe from the dragon's fire. While pushing forward, leave some space for your companions so that you don't block them from engaging the La Valette soldiers.
As you run to the front part of the wooden structure (towards the second), you may notice the dragon on your left, breathing fire onto the structure. Wait until the dragon takes a dive out of sight, then run across the gap to the second structure. This way the dragon won't come up in time to breath fire onto you.
Again, try to let your companions engage the enemies and sneak in a few hits of your own. The main thing is to sustain as little damage as possible while finishing off the enemies as quickly as possible.
Once the enemies are down (or the second structure has been compromised), run into the shelter of the walls. As long as you are underneath the walls, the dragon fire won't be able to touch you. Take care to let your companions pass first, lest you get sandwiched between your companions and enemy soldiers. Once the enemies are dealt with, a cut-scene will occur after which you will have to run across a burning bridge. If you don't run quick enough, the bridge will collapse and you will die.
- Quen is helpful here as it prevents incineration and absorbs enemy hits. However, the dragon fire (not to be confused with the incineration effect) will still be able to damage you through Quen.
- Try to stay out of Triss' way because her fireball will stagger Geralt, making him easier to hit.
- Geralt may dash through to the walls without defeating the defenders. However, those who are not engaged by the others will catch up to Geralt and he will be surrounded more easily.
The next quest of the Prologue is Blood of His Blood.
- Two startling events occurred during the siege of La Valette Castle: counter to prophecy, Goodguest the White killed his brother and not his father, while Count Palatine Rosencrantz stooped to catch his dropping pants and thus evaded an axe headed straight for his neck. Also, no one could have predicted that the Temerians would be attacked by a dragon. Not a forktail, as the scouts had reported, but a huge, angry, fire-breathing dragon. Surprised by the beast, Geralt stood no chance against it on the bridge. He ordered all to retreat to the town, and rushed in that direction himself. It was there, in the temple quarter, that Foltest's children were being held. The king's goal was at once the witcher's.
- We should pay honor to the soldiers and knights of the La Valettes, who defended their lords to the bitter end. They did not retreat, even when the dragon belched forth its devastating fire. Seeking shelter from the heat beneath the hoarding, Geralt was forced to put them to the sword. Once the defenders were no more, Foltest and the others could pass through the gate.
- The La Valette forces had been defeated, but the dragon remained a threat. It came at our heroes with all its might. Showing presence of mind and exceptional ability, Triss Merigold responded with magic. With her help Geralt, Foltest and Vernon Roche managed to reach the bridge leading to the town. There, Geralt did all he could to safely get his comrades to the other side.
- Our heroes survived the ordeal through a bit of luck, but also by staying clearheaded. To this very day, Geralt remembers the events on the bridge as some of the most perilous in his career as a witcher.