Blood Alchemy (Unknown Knowledge)

Alchemy is an expensive and time consuming process that requires rare materials and constant use of magic to form even the most basic of potions. So why do all that when you can murder, maim and add a little bit of magical spice to make a serviceable potion?
In all seriousness, the highly illegal process of Blood Alchemy can be achieved by taking a creature that has an inherent ability that you do not posses, siphoning their blood and, after charging the blood in a magical ritual, imbibing the blood to gain that ability for a short time.
For example, Carl the Human Fighter wants to hunt a white dragon but doesn't want to instantly die to the Frost Breath. So he goes out and finds and Ice Mephit, a minor elemental. After capturing it, he takes it to his illegal alchemist buddy who uses a long syringe to painfully extract the life's essence from the mephit's body. In just one hour, a suitable Potion of Ice Resistance has been created and Carl can be on his way.
The reason Blood Alchemy has been almost universally outlawed is because it gave rise to the Rivermen, a criminal syndicate of monster slayers and kidnappers that have no qualms about performing this ritual on sorcerers, changelings, dragonborn, elves even. This has lead to disappearances and the extinction of magical creatures across the centuries they've been in operation.
For those less morally inclined as to follow the law, the performance of Blood Alchemy Rituals is relatively easy and the ingredients are as follows:
A living creature with the desired ability to be replicated Note: the creature will not survive the process unless going through the Siphoning Ritual first
A living creature without the ability to imbibe the potion Note: Blood Alchemy Potions cannot be used to double natural resistances
A Runic Circle
A Vial to contain the Blood
A twopenny Alchemist at best Note: Like stated above, Blood Alchemy is a rudimentary skill since most of the power comes from the blood, nearly any alchemist can use it.