There are 10 hunts within Barovia that you will need to complete. These hunts come in the form of Wanted Posters, and have three tiers.
The Sister of Fury
Direfang is done as the Tutorial, which you will pick up during the introduction quests to Barovia. To do a hunt, you need to go to Madame Eva's tent once you have a Wanted Poster. When you enter the tent, you will choose your hunt at Eva, and then you have the option of adding Tarokka cards, which will make the hunt harder but give you potentially more rewards. The achievement only requires you complete the hunts, you don't need to add these bonuses.
To obtain Tier 1 posters, you need to defeat the '5 health bar enemies', like Witches, Vampires, and creatures like that. The type of poster that drops is random, and isn't tied to any specific creature. To obtain the Tier 2 Wanted Posters, you need to complete a Tier 1 hunt. Every player within the hunt has a chance of automatically receiving a poster at random when the creature is defeated. If you are going for the achievement, try to fill a group of 5 of your guild members or friends, as you will have an increased chance of getting the posters you need from the random drop at the completion.
When you enter the hunt, you will receive three 'clues' as to the location of where the hunt mark will be. You need to go to each of these locations in turn to fight the creature, and when he reaches a certain health he will go to the next location. On the map, you will see several green x's that all have locations attributed to them. The following list has all of the location clues and locations I've found so far:
The Temptar -- Gates of Ravenloft
The Ghost -- Graveyard
The Beggar -- Village of Barovia
The Thief -- Fell Bridge
The Druid -- Standing Stones
The Necromancer -- The Ruins of Berez
The Shepherd -- The Cursed Meadows
The Mists -- Howling Hills