Keen Smell. The bear has advantage on Wisdom (Perception) checks that rely on smell.

Pounce. If the bear moves at least 20 ft. straight toward a creature and then hits it with a claw attack on the same turn, that target must succeed on a DC 16 Strength saving throw or be knocked prone. If the target is prone, the bear can make one bite attack against it as a bonus action.

Necrotic Saliva. If the bear hits with it's bite attack, the target must succeed on a DC 13 Constitution saving throw or take 1d6 necrotic damage.

Undead Fortitude. If damage reduces the bear to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the bear drops to 1 hit point instead.

Multiattack. The bear makes two attacks: one with its bite and one with its claws.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 9 (1d8 + 6) piercing damage.

Claws. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 6) slashing damage.