Ancient Urban Rat

Legendary Resistance (1/Day). If the rat fails a saving throw, it can choose to succeed instead.

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

Multiattack. The rat makes one bite and two claw attacks.

Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) slashing damage. 

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 4) piercing damage, and an additional 6 (3d4) acid damage.

Acid Spit (Recharge 5-6). The spews out a 15ft cone from it's mouth, all creature's in the area must make a DC 15 Dexterity saving throw, taking 20 (10d4) acid damage on a failed save, or half as much damage on a successful save. If a structure is hit with this attack, it becomes vulnerable to all damage until a creature uses an action to clean it off.

The rat can take 1 legendary action, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. The rat regains spent legendary actions at the start of its turn.

Bite. The rat makes a bite attack.

Move. The rat moves it's full movement speed without provoking attacks of opportunity.