This topic's title is vague, I know, and that is because I have many suggestions to propose about certain monsters in the game and their not-to-be-dismissed hunters. I've already made suggestions for dragons, so we'll skip them. Let's go through the monsters first;
- Necromancers and Megabeasts; Necromancers could be able to create their own megabeasts thanks to a specific workshop that could allow them to do so. Current necromancer experiments only concerns humanoid creatures. The workshop itself could be called a "Creature Factory' or something in the same vibe, and wouldn't be accessible to dwarves unless one of them is a necromancer. Creating a megabeast could take them days, if not months to finish. Maybe necromancers could have their own types of moods? Who knows.
- Forgotten Beasts; as a feature for ubiquitous worlds, some Forgotten Beasts could become their own fully fledged race of creatures. And their origins could potentially be tied to Creation Myths.
- Werewolves/Werebeast; Being major forces of evil, werebeasts could be handled better in the game, maybe have him being conscious of his own transformation, or behave the same even while transform. During world-gen, some rules could come in play as to how Werebeasts could function. For example; werebeast could be aware of their current form and act peacefully when among their peers, and even transform at any time out of sheer will. Some can't control their transformations and become stark raving mad when turned into a beast. Some wizards/sorceresses (since they're going to be in the 'next' update) could turn people into creatures indefinetely or temporarely. Etc, etc. (Thank Discworld for the idea)
- Vampires; Vampires could be more likely to form a cult/hidden society to organize themselves better and leech blood out of people/animals without being noticed. In fortress mode, some groups of vampires may gather around in a usually unoccupied guildhall/dinning room to discuss and their matter. Checking their activity will just say that they're currently debatting, but without any further detail. Some vampires with the hunter role may go out of the fortress for a while and return shortly after with 'fresh meat' for his fangy counterparts.
Vampires will be extremely eager to reach a noble status, so they could justify/legalize their presence, and also get more meat for their vampire comrades.
If your dwarves are fully aware of their existence, the mayor, or the rest of the fortress, may vote for the cult to be disbanded and its members to be killed, or they will simply accept them as part of society. The King/Queen may decide whether or not vampires should be accepted in their kingdom.
Maybe due to their outcast state, they may develop their own culture surround death and the macabre, and adopt some strange habits (like sleeping in coffins, duh). - Magma Man and other 'rare' men creatures; Dwarves could end up in new types of caves inhabited by these people. Whether they be made of magma, metal, gem or rock, they will thrive in the underground and could be intelligent. Considering that magic will be a major game-changer, they could be tied to it and have special randomized properties. Maybe even have their own pets? Anyway, the level of their civilization could vary, they could be savage, to tribalistic, to similar to any other civ, or extremely advanced (in the vibes of Atlantis).
And now, the Hunters;
- Exorcists; a new type of hunter, that could be entirely tied to religion, who could be living or traveling from fortress to fortress to keep the living from evil forces. Possessed dwarves with very dark moods could be cleansed from their macabre thoughts thanks to an exorcist. Exorcists could also be tied to medicine as they could probably find a cure for dwarves/humans/elves infected with werebeast syndrome. Maybe removing a venom and putting it in a goblet/bottle? Their exorcisms could go from religious feats to full on combat with the possessed/werebeast, though they will never attempt to kill their target.
- Vampire Hunters; May they be dwarves, humans, elves or literally vampires themselves, they will travel the world, from town to fortress, to find vampire cults/specific vampires. Their role would not only consist of hunting vampires, but also treat the victims of vampires. For instance; if a dwarf has been bitten by a vampire/became a vampire, the hunter will immediatly come to him and talk about the side effects of becoming one, or even propose to join him in his hunting shenanigans.
- Regular Monster Hunters; if a specific monster becomes way too prolific, some hunters may become specialists and hunt them for a living. If your fortress is flooded with them, they may ask to join it and accept to hunt them down in exchange for a home. Some liaisons may talk about their services and you could ask them to send in one in your fortress, who will stay in your fortress for a while, waiting for the monsters to come. They may ask for payment with cash, objects or trophies.
- Megabeast Hunters; These lads could be legendary hunters, wielding impressive weapons that no other mere mortal could even lift. Some could be demi-gods send by gods to get rid of a specific menace, like a forgotten beast who has destroyed some many fortresses and possesses one as a lair, or even protect the god's followers from said-menace. Or they could just be legendary hunters who have made their reputation over several notable kills, notably killing beasts who slayed kings and barons and several legendary knights. They wouldn't be too tempted to join your fortress, as they may be the rival to a demonlord, or your fortress just doesn't have many forgotten beasts around.
- Dragon Hunters; More or less the same as Regular Monster hunters, but they could pick up dragon eggs and dispose of certains drakes living in specific lairs.
- Groups of hunters; if one wasn't enough, many would do the trick. Each member could have its own utility to the team, like being a medic or a monster specialist, but what makes them effective is their teamwork. Alone, they may not be as effective against monsters. They could have a leader, or just work hand in hand as friends, taking decisions democratically.
Phew, that was a lot to write.