The item says any enemy character so am i right in assuming it can target an assassin type character before he reveals himself.
I don't think so. You can target any character, but you have to know he's there. I mean, I suppose...
I would have to say no. Assassin would be treated as character in reserve for purposes of example. You could not target a character that was being held in reserve because he/she has not officially entered the playing field. But as soon as he pop his pointy eared little assassin-ny head out “NUKE EM!” I hate those guys.
It is actually entirely dependt on how the particular Assassin's "Hidden" Rule (or equivalent) is worded. For Dark Elves, The Blood Statuette doesn't care whether or not a character is on the board, "revealed", etc. You just pick a character. The character needs the exception to its effects.
But how do you name a character that you don't know exists. It'd be meta-gaming to note he has an assasin figure around somewhere, or your buddy always bring ones. (Metagaming is frowned upon in D&D, is it common practice in warhammer though?) Lastly if you named an assasin and he didn't actually have one on his list would it be lost?
Well, you see, Warhammer Fantasy isn't at its core a roleplaying game. You don't show up with armies made up of unknown points, so that sometimes it is 1,000 vs 2,750. Anyway, where I play at, you may look over each other's lists before the start of the game in pick-up matches (Because we all make mistakes now and then). I even specify which hero has what magic items so that no one claims that I'm teleporting them around (you don't actually have to say what magic items a character is carrying till they are used). Now, in tournaments, where army lists are reviewed by non-players before the start, yes, you wouldn't know that he happens to have an assassin till he reveals it. But again, DE assassins at least have in-built protection from it. If the others do not (unlikely), and you know that the list has that kind of character, and you aren't playing some super-serious RP campaign, then there isn't any reason why the statuette can't target them. Heck, to make it not meta-gaming, a skink priest read it in the stars that there'd be an assassin there, which is perfectly in line with an army preparing for battle with seers available. EDIT: To make the meta-gaming thing more apparent, unlike DnD, when your General dies, you don't automatically lose. You aren't playing a character, or even from a set perspective. You making moves is an abstraction of the entire military network of your army and its logistics doing things.
Um the list must say if/how many assassins are present as they are characters, he must not however say where they are. Edit: I'm not sure on this but i think he can decide in which unit(s) they go after deploying even.
Well, it doesn't have a spell type, so it follows the "generic" restrictions on page 31. Which it will probably fulfill at the start of the game (when else would you use the Statuette)? EDIT: And the (DE anyway) Assassin is assigned to his bunker unit at the "Start of the game", which you need to make a note of, because he can't teleport around.