I can't even remember taking the notes that i try to decipher now. A. is NOT invisible. She is not even well camouflaged, but she erases the memory of her. Probably. It could also have been some other Monster and A. just created that mindfog. A. is very, very dangerous, because she can inflict crowds that suddenly agree that history was different. She alters peoples minds, sources and evidence disappear or declared a hoax. Some people seek her out in the hope to erase painful memories. A. herself is not that dangerous, but the conflicts she leads to, rarely end peacefully. She is the third form of Memoryghasts. The other two are Memorexia and Obliviti.
How to fight it
If you fight a community A. you will most likely be killed by the mob not wanting to remember the truth. I am not sure if there is a way to tackle A. directly.gab