Fool's Scorpion Grass

Scorpion grass, myosotis, mouse's ear. There are many names for the plant colloquially known as the forget-me-not, a small blue flower with five petals and a small yellow pistil. The little cerulean plants are so named for their tendency to grow back year after year after they've seemed to fade out. These flowers, are of course, entirely harmless, and despite technically being a weed, looks spectacular as bedding in one's garden. However, one should always be careful when encountering a forget-me-not that it doesn't have a small purple glow at its heart. For if it does, you've encountered the true scorpion that lies in the grass.
Mentisotis (also known as "fool's scorpion grass" and the "forget-me-plant"), is a magical plant which is thought to have begun growing throughout Aurore around five-hundred years ago. Scholars note that this date coincides closely with the beginnings of the Aspaxian Empire and some theorize that there is some correlation there. Regardless of their origins, the effects of the forget-me is not disputed. When pollen from a specimen of fool's scorpion grass reaches a sapient creature, it will have a slow but building anti-memetic effect. The symptoms of passive inhalation of fool's scorpion grass begin small, with memories like what one ate for breakfast being lost. But if left in contact for an extended period of time, larger and more important memories can disappear.
While a single large dose of forget-me pollen immediately erases one's short term memory, low-dosage long term application has a much more sinister effect. Rather than indiscriminately erasing every memory, it seems forget-me pollen can specifically target the memories one consider most important to themselves. The forget-me also covers its tracks. For example, if a loved one is targeted by a forget-me in a subject's memories, the subject's memories can be altered so that past events in their life did not include that loved one. Research has been somewhat successful in changing the target of a forget-me to a specific type of memory, and this has been utilized by a number of clandestine organization.
But perhaps the most sinister effect of the forget-me is entirely unknown to nearly every person that has studied it. Both long-term and extremely concentrated exposure to a forget-me can kill a target. If a target is killed as a result of this pollen, they will be immediately wiped from existence. Physical evidence of them existing still exists, yet none are able to perceive this evidence, and all memory of the now deceased individual will be rationalized to fit this new reality without the departed. Instead, all they notice is that pretty blue flower, swaying in the wind...