This is an occult state that came with Supernatural EP.
They live 50% longer than "normal" Sims.
Sims can transform from Human to Wolf form at any time, but during a Full Moon they are forced to transform to Werewolves, during this time they'll get the +40 mood boost, just like other Sims but cannot revert to human form. While in Werewolf form, and growing hungry they get a Hungry Like the Wolf moodlet and can eat fish and other foods raw (though some are not edible for an unknown reason).
Your Werewolf can Hunt the world for Gems, Insects, and Metals. Werewolves can make a lot of money buying one of the new Gem Cutting Machines. They can Hunt Solo by clicking on the ground. They are able to hunt in packs with other Werewolves, which increases the rate at which they'll finish hunts. Packs are formed much like groups, with Sims needing to be on the most basic friendly terms to accept. You do not need to have Sims in your household to form a pack, and the pack leader (whoever queues Hunt with Pack interactions) will get all the loot. When the hunt specific items ability is unlocked at level 6, your pack leader can pick a type for the focus of the hunt. Stay on the lookout for collectibles you can grab manually while your Werewolf is out hunting!
Werewolves benefit from the Gatherer trait if they cut gems, as they can make more money but it doesn't seem to affect the outcome of hunting.
Simply hunt for items and use other Werewolf-specific socials and actions, and gradually gain ability as a Werewolf. They will find more and better items using Collect and fail at howling less often. While Werewolves' Lycanthropy hidden skill has ten levels, only a few of them register and show a level. So, any stated levels will be there only to show you how far you might expect to go before unlocking each ability:
Levels 1-10 Hunting Improvements: As you level your Werewolf, their senses will be honed, allowing them to easier find items. You can find up to four items at once as a high level Wolf. So, while you won't see a notification for every level you gain, know your Werewolf becomes better at finding things as you use abilities. Werewolf skill does not show up in the usual place but you may see a blue bar increasing over his head.
Level 3 Cursed Bite: Your Sim attempts to bite the target and curse them with Lycanthropy. This interaction can fail but will be guaranteed to succeed with the Alpha Wolf lifetime reward. After two days, the initial bite moodlet will disappear and the Sim will transform for the first time. My Sim was able to bite his (human) wife and it was accepted.
Level 6 Hunt Specific Items: This will let you find Gems, Metals, or Insects specifically.
Level 8 Anger Management: The Werewolf is less likely to transform when angered.
Level 10 Full Potential: No specific perks to this last level, although Werewolves will be less likely to fail at bites and howls than they once were.
This Lifetime Reward costs 20,000 Happiness and ensures your Sim will no longer fail at Cursed Bites or Growls. The Terrifying Howl interaction is added, which can be used at daytime unlike Howl at the Moon and can cause Sims to faint and take a -20 terrified moodlet for an hour.
Even a top-level werewolf can savage Bigfoot, and will win the fight, but Bigfoot will not change.