I am on my first playthrough, and just started Act 1
During the Prologue, I let Aryan surrender, and so ran into him during the dungeon escape. I got the cut-scene where he breaks free from the guards bringing him back to his cell. I went to clear the upper passage, then returned to carry him up to the oil room to open the secret passage-way and start the fire. Then I left...

I just read that there is a torture room off the cells with an executioner to fight. Since I didn't do this, is there anything important I missed? Is it worth going back to a previous save to do this?

Cheers!

If you did that,you wouldn't be able to take the route you already took.Do it on your second playthrough.The answer is-no.

You can clear the room and kill the executioner even if you saved Aryan. But if you didn't, you're not missing anything important apart from some junk and few exp points.

If you take the upper path, you get to use the trap door to reach the executioner's room.

That is, when the guard who says the wind blows hard, knock him out and go upstairs. Knock out the guards there and get the key. Then go back to the door near the stairs, and use the trap door in the small room.

Ok, thanks to all for the responses!

Yes, I knew there was a 'high' and a 'low' road path through the dungeon. I'll try the other route next time...

Cheers!