Flaygian's notes are obtained during A Taste of Hope. They are the results of Flaygian Screwte's effort to translate the Haemalchemy book that the player found during Darkness of Hallowvale. It contains the some notes about the vampyre's immunities, and Screwte's theories on how to overcome them.
I have been translating the Haemalchemy book for some time now. While the book contains a lot of information, the thing that's most interesting are the details on vampyre immunities. According to the book, these immunities are a result of two factors, both of which we will need to overcome.
The first factor is the easiest. Any weapon not made of silver has little effect on all but the weakest vampyres. Because of this, any weapon we create will need to contain silver.
The next factor is more complicated. The more powerful vampyres apparently possess the ability to predict and dodge any attack. This seems to come from a combination of their fast reaction time along with a limited mind reading ability. To overcome this, we will need to create a weapon that attacks in unpredictable ways. If the vampyres don't know what the next attack is, they won't be able to avoid it.
From my research, it seems that the weapon we will need is a flail. Flails are said to be very unpredictable which should make them perfect to use against vampyres. While the flail will need silver components as well, I suspect we'll need to reinforce this to ensure the flail doesn't break.
Three components will be needed in total, a shaft, a head and a chain to join them together.
Members of the Myreque have recently managed to recreate the Rod of Ivandis. This rod is known to be very effective against juveniles and juvinates so will probably make for a good shaft.
For the head, our own symbol, the silver sickle, seems like an obvious choice. We'll want to reinforce the sickle with an emerald enchantment to increase the effectiveness.
The chain won't need to be anything special, we'll just need to make sure it doesn't break.
It goes without saying that all of this research is purely theoretical. The only way to be sure of this is to create the weapon and test it out.