High level assassins are a lot of fun. I used 3 of them to exterminate the French royal family over a period of 10-15 turns, as half of the cheezy finish to my English short campaign (the other half being lightning amphibious raids on Scotland's 2 cities). I had surprisingly good luck, succeeding many times with 30-40% chances and not dying even after trying plenty of times with 15-30% chances.