It looks like a good sub so far, although personally I would ditch the entire "Immunities" section, (A bit too stat blockish, like you'd find in a D&D monster manual for my taste) and work the info into some type of anecdotal presentation to make it more fun for the reader and less dry.
"Renthwrith and me thought we could take out a blood beast easy as skinning a drowned rat. I hit it with some charming magic to make it hold still and Renwrith pumps it full of poison darts.
Unfortunately the damned thing seemed to ignore my spell and his darts didn't do much more then draw it attention; away from me back towards him. What'd I do? I cut my losses and ran for it! Last I seen, Renwrith was trying to fill it full of arrows as it charged his hidey hole in the rocks. Haven't seen him since..."
It seems to me that with these creatures being so powerful, so difficult to kill, and so easy to multiply, that they would quickly overrun an area. That would definitely be a good plot hook on its own. The players could be given clues as to the wizard who created them and then try to find something in his notes to help destroy the blood beast infestation.
This not just an excellent GM's tool but an excellent players tool as well. This amplify the traits of the character, as IF-J says some players have different instincts. This forces both the player and the GM to wonder what the character is thinking and then amplify the results. I wish you had written this years ago.
First off, I must say that I like the idea of this blade a lot. After all, what better way is there for a GM to give the party hints or point out the (blindingly obvious) clues that they always seem to miss? However, I would really like it to be a little better defined.
I think my main stumbling block is the source of the "hunches" or "ideas" that a PC gets. Does the player have to state the hunch out loud? Does the GM assign them based on a random dice roll, perhaps modified by the character's intelligence? Does the sword get these hunches on its own?
Without a clear idea of the hunch that the sword is trying to prove, I think that a player could become lost really quickly, not understanding what the sword is supposed to be doing. If this central concept is codified a bit more cleanly, this submission would easily move from a 4 to a 5 in my mind.
Very clever GM tool! It's fun thinking that players could feel like something would happen if they kick this tripwire only to be greeted by a nasty trap if they do. Even better, they could feel compelled to say something rude to a half-ogre, receive a minor beating, and then receive help and/or praise from someone who can aid them in their current mission. I really love that this sword can be as bitter as it is sweet and can help as often as hurt. Good read!