I probably play too much WoW TCG, but I have a question about attachments. Is there a limit to the number of attachments, or the types of attachments that can be on a character? I can't find anything in the Core Rules, but I wanted to make sure I wasn't cheating by putting two copies of Blood of the Dragon on my Khal Drogo.

As a base rule there are no restrictions about how many attachments a character can have. If there are any restrictions you'll find them on the various cards. For example the "No attachments" keyword is of course a limitation as is "No attachments except Weapon" or "No attachments except Boon". Then there are attachments that say things like "Targ character only" or "Ironborn character only" for example.

If no such restrictions exists on any of the cards you play then you can go ahead and beef up a character how much you like.