So many blood mages.

Due to the heavy violence of Kirkwall's past as a Slave Sale Market for Tevinter Magisters and the crazy magic they did in general, the place itself has a very thin veil. So what may be whispers of demons in Ferelden may be clearly heard words in Kirkwall. I think people have likened it to the City being near a Hellmouth, so shit just goes down there 20 times more than elsewhere.

Also, due to Meredith's way of handling mages, there was a lot of pressure for mages to either escape or kill themselves. AS much as Anders probably thought he was helping with the mage underground, exactly where were those mages to go once free? they weren't spirit healers, capable of keeping the local villagers happy with healing their son for free in exchange for not telling the Templars where they were. They had no currency, they had no idea how to take care of themselves. That fear drew demons, demons who told them how they could get the safety from the Templars they needed.

Kirkwall has a Hellmouth and it's full of bad mojo, makes everyone crazy.

Look out for messages from the band of three. They were scholars investigating the violence in Kirkwall. Apart from blood mages you have a lot of serial Killer and other violent persons.
Its mostly because of phorays explanation, but there is one more reason, the measages only hint at and you find out in one of the dlcs.
The messages are called 'The enigma if Kirkwall' they are everywhere in Kirkwall and outside.

Another implication is that Meredith's heavy-handed approach means that most Templars (but not all) tend to treat any apostate or escaped mages in Kirkwall as a potential Maleficar, so the Templars rarely plan on taking in suspects in alive.

By making every engagement with the Templars a matter of life-and-death, many mages in Kirkwall might be tempted to turn to blood magic because it was preferable to being killed, thrown in the Gallows (again) or made Tranquil.

Especially when you remember that you can be made Tranquil in Kirkwall for passing love letters and even lesser offenses, while some Templars (like Ser Alrik) were abusing the Rite to create their own personal sex-slaves.

It says something that in Kirkwall, being a blood mage is considered safer than being in the Circle.

Otto Alric is the Templar, who requested the Tranquil Solution, Tranquilized Karl, and wanted to make Ella to Tranquil, and Tranquilized other mages too to be sex slaves


And there's Karras, who visited Alain's (Starkhaven apostate) chamber...:

These just random scenes, if Hawke speaks one-two mages/templars at the Gallows, or just watching for the conversations.

I missed many of them! Not just little NPCs' conversations, but for example a full scene (with or without a little battle), if Hawke let Feynriel go to the Dalish, a Templar squad go for him to the Sundermount. It turned out, that the Templars tortured an elf, to speak about Feynriel, and planned to torture more, if don't hand over him. There are many interesting stuff, I didn't see before.

Yes, the elf-blooded boy from the Alienage. Interesting quest, I like it. I love Hawke's conversations with the companions after the Fade...

Don't forget to visit them! Someone of them will excuse, someone of them will blame Hawke. Anders is the most interesting if Hawke deals (or tries to deal) with the sloth. At the moment he's able to stop the flirting or break up if they're already in love. Fenris' reaction depends on rivalry or friendship, Aveline also interesting... I tried in the rivalry, with a mage, but I heard, his conversation doesn't change in friendship – I'm not sure about it.

Ah yes, Kirkwall, i'm very fond of it, riots, theft, plagues, mages getting their ass kicked and much more, good times.

Karras can die in the Act1 (my current Hawke killed him for example), but probably not he's the only one, who knew what's Meredith's plan. 

But yes, not this would be the only case. (And later, in 9:40 happens in Rivain: the Seekers annulled the Dairsmuid Circle, because the mages there lives in a family, and trained the apprentices to the tradition of the seers.)