Quote Originally Posted by BloodSquirrel View Post
Severing heads is mostly just fluff- mechanically, it's instant death. Bleeding is just HP loss- there's no separate mechanic for a person suffering from the blood loss itself. Scar tissue is just RP fluff
There are a few cases where severing a head doesn't result in instant death. Hydras and chimeras are obvious examples. I'd be surprised if someone hadn't brought a Pierson's Puppeteer into a D&D session at some point; as shown in Ringworld, decapitation for them is a serious inconvenience rather than being fatal. ("You tied a tourniquet around his neck, doctor?")