Brane Food
This unsubtle assassination tool is banned in most planes of existence for being remarkably indiscriminate. Brane Food is essentially a magically mutated form of the cashew apple that has been further been manipulated in space-time until it’s just plain wrong. Then it gets steeped in a pool of evil for a week or two. When it starts to bubble and look for a victim, congratulations; the Brane Food is ready.
Brane Food works by being frighteningly appealing to human brains. Extremely so. So extremely so that the brain will itself attempt to break through its own skull and ‘attack’ the Brane Food. This, of course, never actually happens except under the highest of magical background levels; which is good, because the sight of a disembodied brain flopping around with two eyestalks while trying to crawl to its quarry is a sight that most people don’t want in their heads.