Ratatoskr, Variant (5e Creature)
From D&D Wiki
Tiny beast, unaligned
Bite. Melee Weapon Attack: +2 to hit, reach 5 ft., one target. Hit: 1 piercing damage.
Scurrying in the underbrush of mystical forests are rats with sleek, kempt fur and a single short horn stretching from their foreheads. These ratatoskr live in constant fear, constantly being preyed upon as the lowest step on their ecosystem. They are capable of being understood by all that would hear them, and while this is rarely helpful in their survival, it causes them to commonly be kept as pets by their less animalistic cohabitants.