Homebrew (based on the official Rat statblock)
Stealth +5, Survival +2, Acrobatics +3
Darkvision 30ft; Passive Perception 10
Keen Smell. The rat has advantage on Wisdom (Perception) checks that rely on smell.
Bite. +0 to hit, reach 5 ft., one target. Hit: 5 (1d4 + 2) piercing damage.