Bestiary: What. How. When. Cast your vote!

Very nice poll.

Agreed. 

Final Fantasy XII does this. after killing an enemy a number of times, you unlock the "sage knowledge" that allows you to read additional information about the enemy such as its lore, the posible items you can get from it or a cool story about an adventurer/explorer and how he/she discovered or fought the monster. Some enemies will have large stories that you can only complete by defeating many different types of monsters in a level or monster of the same species. i loved them.

Having each bit of information locked behind a certain number of kills sounds like a good incentive to not bypass them (unless you're doing a Speed Run).

Bestiary should be available from the start of the game in the menu and accessible at any time (most likely a tome given to Miriam by Johannes--he found it, but has no clue as to the black silhouettes or what they mean). Locked entries should have a black silhouette and "?" for the name and weaknesses/strengths/battle tips. Once you attack an enemy, the silhouette becames a hand-drawn image of the beast and the name appears, but no other information until you kill at least one of them. Then everything is shown (weaknesses, etc). All information should be carried over to NG+.

Very well done! It's most everything I look for in a Bestiary. The only thing that I would add is what hyugakojiro already mentioned.

I am only slightly surprised that this hasn't been addressed at all in any official posts or updates (that I can recall). My guess is they are saving such info to closer to launch. I would be extremely surprised if it didn't make it into the game, or it is in the game but the developers fail to mention it.

Killing a creature over and over for more info is a neat idea. It's an incentive for trying to farm that one shard you just can't seem to acquire, plus, helps you unintentionally acquire rare drops. Incentives are always cool.

Voted and want to comment / justify my choices:

A. You carry a (passive) Tome with you, you can reach it anytime in the menu.
Although i do like the idea of actually finding the bestiary, i loved what recent games made, by adding the bestiary from the start. Usually, when the bestiary is an item, although VERY EASILY to be found, there is still a chance the player may not get it (unless you do it in a way where it is impossible to miss by physical means). Considering Bloodstained has lots of things dependant on enemies (the drop of forging materials, Shards, etc) the bestiary is almost mandatory to play it in a sucessful manner, so, i think it makes more sense if you start with it.

B. The Bestiary contains a 3D-models. You got control of the camera-angle.
That is a given. The game is 2.5D, all the enemies are rendered on 3D, and they actually have a lot of cool and interesting details when you look closely, so, i think it would be awesome if you could see their models and look around them in details.

C. You unlock more and more info, the more you kill THAT creature.
At first, i thought this wasn't a good idea, but rethinking it, i thought "you know, that could be fun, from a completionist point of view". Some Igavania games were already like that, when it comes to drops (where all drops shows as "??" until you get them). I think HP, EXP and such could be given if you kill it for the first time, bu maybe each enemy could have a small number of "kills" in order to reveal everything else (strengths and weaknesses), that would give the player a "small quest" to kill all enemies "X" number of times to reveal everything. (That could be combined with the fetch quests to kill enemy X times from quest givers too).

D. Info are carried over in New Game Plus along with the Bestiary.
It just doesn't make sense to have a new game + if you can't bring the bestiary with it.

E. Creatures yet not engaged in combat shows a blank page (or similar).
No sillhuete. Let the hidden and the secret, be secrets until found.