the guide contains answers to the puzzles and possible spoilers

at one point the emperor will tell you that any legends about a dragon underneath the city is a lie. i hope we all understand here that the emperor is not really trustworthy also. there IS a dragon, and we are going to find him.

to enter his location you need to go to the wyrm's rock prison and have any lighting spells ready.

here is the instruction how to open the hidden door to the wyrmway

inside the secret passage you will find several doors with the trials. you need to do them to earn the right to face the dragon.

this is chamber of courage - a fighting trial.
you need to pick up the blue torch and survive for 4 turns.
keep in mind that the one character who has the torch will become the main target to the enemies and if he dies, the challenge will fail.

overall the fight is not too hard, just remember that enemies will spawn for 4 turns and try to kill as many of them as you can each turn.

here is my fight with them on tactician, i have the most boring party of vanilla classes: fighter-thief-cleric-mage, i think the most useful tactic was to keep the character with the torch near the guardian of faith summon, who does half of the work.

a gimmick challenge. you can waste your time trying to catch the flying books and yada yada, or you can just shoot the one npc i show you here and be done in literal seconds.

here you need to solve the chess puzzle. i am not really good in chess so just to be safe i'll assume that this puzzle may have several solutions? it would't surprise me.
anyway, the video below is the solution i managed to come up with. let me know if you got a different one, i am curious.

in this room you can look at all the portraits on the walls and learn about a thief who did some good things and some bad things. your task is to decide what punishment he deserves.

to do that you need to chose the portrait with the punishment you want and put it to the slot.
the problem is, all these portraits are cursed.

the curse means it can be removed, right? so this is shadowheart's time to shine with her remove the curse spell.

the right answer is prison - the thief did some good after all, no need to execute him. also you can't let him go free because he did stole some artifacts.

here is how it played out

ansur is the dragon boss. to get the achievement you need to kill him while he is up in the air. he does that every several turns oh so. your main task is to lower his hp as much as you can so when he will eventually fly you'd got a chance to oneshot him.

ansur is the lighting dragon. i entered that battle without any knowledge about what's ahead and won mainly because of my butthurt and a bit of luck - astarion had the ring that grants the immunity to lighting.
even with a half dead party i managed to slay ansur and get the achievement. if you can resist the lighting damage, you'll be fine.

that fight and the ring i used on the video: