IndigoGolem
The Destroyer
Equipping a voodoo doll as an accessory should redirect 50% of damage you take to that doll's NPC. If you have both dolls equipped, it prioritizes whichever is in a higher accessory slot. Killing them this way can summon Skeletron at night, or WoF in hell if it's lava damage. I don't see this being overpowered because the Guide and Clothier can only take so much damage before they die and you start taking all your own damage again. If it still seems unbalanced, this damage should give them reverse invincibility frames that stop them from being healed by the Nurse for a brief time after taking damage.