Build a Necromancers Throne and create a Necromancer, then get a Ronin with a Blood Bond battle gear. Blood Bond him with the Necromancer, then send the Necromancer up into a Watchtower. Fill up the Necromancers Throne with four more Ronins, then send the Blood Bonded Ronin to the enemy base and see him die. When you look at your Necromancers Throne you should find that you have a new Necromancer. Repeat this if needed. Note: A Geisha, allied or your own, must be nowhere near the Watchtower.