Did this with the Silent: On starting a new run choose the "first three combats all enemies have 1 HP" option then when picking the starting room pick on with a shop close to the bottom, so you can get in and out without finishing three combats. With some luck the shop will have a skill card available that applies poison, which you can use to complete then next combat without using any attack cards. Only took me 2-3 resets before I was able to complete this setup.