"Ms. Pearsly? Where are you going?"
Melona looked over her shoulder to see Professor Sneayc Oyle approaching her. The half-elf woman had a quizzical smile on her face. Ever the consummate actress, Oyle had as much of a talent for expressing a thousand words in a single expression as she did for brewing potions. In this case, the thousand words she was expressing began with "Why would you do this, you silly girl? Go back to your station and let me use this as a teaching moment."
Melona didn't bother answering. She just did as her professor's smile commanded.
"Okay, class, gather round!" said Sneayc. "This is a teachable moment." Inside her skull, Melona let out a groan of utter humiliation. She didn't want this to be a teachable moment. She wanted to crawl into her own robes and vanish like a ghost. "Now, while a putrid odor is never pleasant, least of all from a potion you're making, it's actually a sign that your problem is eminently solvable!" She laughed, and the class laughed along like a Manavision comedy audience. Melona didn't understand why. That wasn't a joke. It wasn't even amusing. But then again, Sneayc was a genius at doing forms of magic that, seemingly, required no magic, and charisma was the oldest of those disciplines. "Now, Melona, can you guess why you might be getting a smell of rotten meat from your potion?"
Melona sighed. "It comes from a combination of necromantic and biological energies within the potion. Alchemical magics are more sensitive to negative influences, so while you'd actually need a considerable amount of mana to cast a spell to make something physically rot, even a lack of life force, metaphorically speaking, can cause what's called 'alchemical vitiation.'" She had gradually transitioned into the textbook passage she had memorized by rote; it was more or less a word-for-word regurgitation of what she had seen.
"Someone's gonna get full marks for their reading assignment!" Oyle laughed again. "But the book didn't say how to fix the problem, did it?"
"No, Professor," said Melona, feeling irritated. "No it didn't."
"Well, let me take over, then!" She flashed the class a smile bright enough to incinerate an army of ants. "Now, there are two things that you can do here. The first thing is just to infuse your mana into the potion." Sneayc looked at Melona, and for a moment, Melona could swear that the expression on Sneayc's face was one of genuine, unrehearsed pity. She looked back up. "But if you can't do that, you can always use what the women in my family called 'Mama's Monthly Helper.'" She pulled out a small needle from her robes. "Blood!" The class gasped in sincere, but theatrical, shock. She held the needle to the fire, letting it heat up, then pulled it away when it got hot enough. "Now, there are four things to note here. The first is, you want to use your own blood, or the willingly-given blood of a sapient creature. Don't use animals, now! It's cruel and it won't give you the energy you want. Second you want to sterilize your needle or knife. You don't want to get an infection!" The class tittered a little. "Third--" Sneayc held up a ring finger and gently pricked it, wincing as she did. "The extraction process isn't any fun." She held her bleeding finger over the cauldron and let a couple drops fall in. Almost instantly, the reek faded, prompting raucous applause from the class. Sneayc held up her hands in appreciation, then gave a gesture that Melona saw a conductor use to get an orchestra to stop playing. The applause stopped.
"Now, this is important. Blood carries positive biological energies, but it's also tainted with the conscious intent and subconscious desires of its source. That's why you don't want to use an animal or, gods forbid, human sacrifice for a potion! If you've taken the blood from yourself, it'll typically be fine, but even then, you can get some unexpected effects! For instance, this potion--what did you say it was, Ms. Pearsly?"
"I didn't," said Melona. She was embarrassed to admit what she had been making.
"Well," said Sneayc, evidently feeling merciful enough to not press the matter, "this will be a double-surprise then! How about...