It is made by adding to a vial of water a guam leaf, jangerberries, and ground bat bones, in that order, and then bringing the resulting potion to the Watchtower Wizard to enchant. Making the potion requires 14 Herblore. This item will disappear when dropped. Before dropping the item, it will ask for confirmation, stating: "This item will likely break if you put it down here, and you will have to go looking for another."
After using it to kill the last Ogre shaman it will become an empty vial. The magic ogre potion cannot be made after the quest, and if one is brought to the Watchtower Wizard, he will confiscate the potion, claiming it is too dangerous.
Using the potion on an Enclave guard won't have any effect, but it also doesn't produce the normal "Nothing interesting happens." message. It's possible that a unique interaction was planned but never fully coded in.