The winter update of 2017 introduced new features to Tibia 11. One of those was a promising bestiary, one of the three parts of the Cyclopedia. It includes slots for every regular creature occurring in the game, unlockable in 3 stages.

The following table shows the number of kills you need to have of a specific difficulty creature to unlock the next stage. If you manage to fully complete a slot for a particular monster, you will be rewarded with some charm points.
As far as Rookgaard is concerned, only a couple of monsters exceed the trivial level (Bear, Deepsea Blood Crab, Ghoul, Minotaur, Minotaur Mage, Orc, Orc Spearman, Rotworm, Skeleton, Tiger).

After killing the creature for the first time, the slot will be revealed, showcasing the monster's name, sprite, and difficulty level.

If you complete the required number of kills for the first stage, some basic information about the monster will be included in the bestiary, such as the monster's hitpoints, speed, defense, attack, and common loot (over 25%).
After completing the second stage, the information will be updated with the monster's weaknesses and strengths, as well as where it can be found and its uncommon loot (between 5% and 25%).
Fully completing an entry in the bestiary updates the information with semi-rare loot (1% - 5%) and rare loot (0.5% - 1%). Any items with a chance lower than 0.5% (very rare) will only be revealed after actually looting them from a monster.
The process of filling out your bestiary is linked to some achievements, one of which you can even get on Rookgaard!

Hunting Permit (1 point)
You have fully unlocked your first monster in the Bestiary.

All the difficulty levels of monsters inhabiting Rookgaard were tested during a test server by Bogus Rookstayer. He also managed to answer all of the questions we had concerning the bestiary - thanks!

Q: Do quest monsters such as the Spider Queen have their own bestiary entry?
Q: Can you get points for killing hyaenas summoned by Apprentice Sheng?
Q: Are bosses a part of the bestiary?

Bogus Rookstayer: No.

Q: What happens to your bestiary after you get rooked from the mainland?

Bogus Rookstayer: Everything stays in its' place; completed entries, charm points, as well as purchased charms.

Q: Can you get charms on Rookgaard?

Bogus Rookstayer: You can only get a total of 170 charm points on Rookgaard, which isn't enough to buy a charm. It is, however, possible to get the charm points on the mainland, purchase a charm and rook yourself.

The additional goal of fully completing your bestiary and the achievement connected with it are a perfect way to have something to do on Rookgaard. Fully completing a monster is satisfying and a pleasant way to obtain some experience and get closer to the next level.