This magical belt is covered with werebear fur. While you wear it, you have advantage on saving throws against being charmed or frightened, and you gain the werebear's Keen Smell trait as well as proficiency with Perception. You also gain a Strength of 19 if your score isn't already higher.

Keen Smell. You have advantage on Wisdom (Perception) checks that rely on smell.

Curse. The belt is cursed, a fact that is revealed only when you attune to it. The identify spell is deceived by the curse and falsely reveals the item to be a Belt of Hill Giant Strength. Attuning to the belt curses you until you are targeted by the remove curse spell or similar magic; if the curse is removed, your attunement to the belt also ends. While cursed, you cannot remove the belt, and you refuse to wear any other belt. You also have vulnerability to bludgeoning, piercing, and slashing damage dealt by attacks using silvered weapons. Finally, during nights when the full moon is out, you experience all the effects of the curse of werebear lycanthropy following the rules described on page 207 of the Monster Manual, including gaining damage immunities, the shapechanger trait (which absorbs this belt into any forms where it doesn't fit), and the change to your alignment. Your DM is free to decide that this places your character under DM control until the sun rises again. During this period, you are able to pass on the curse of lycanthropy just like a true lycanthrope.

Notes: Set: Strength Score, Advantage: Saving Throws, Advantage: Perception, Proficiency: Perception, Buff, Cursed, Belt