The last potion was to clean his blood. The dark poison oozing around in the scar on his face was infectious, it had to be controlled, to stop it spreading to other parts of his body. Well, as much as that potent a level of Dark Magic could be controlled. The stench from his scar right now was utterly vile. Genuinely, gut-churningly offensive, you might say. The rancid smell lingered in Harry's throat and he dry retched at it. It hadn't been cleaned for three days, he remembered, and there would be consequences with that.