Skaven

ability score increase: Wisdom +2 Charisma +1

age: Matures fully at 6, can live up towards 80+ (usually don't)

Size: Medium

speed: 30ft

Languages: Common, Queekish

race features:

Pack Tactics

Preferring to work in groups, the skaven gains advantage on attack rolls against another creature if one of their allies is within 5ft of the creature being attacked.

Fearful

Skaven are naturally fearful unless trained hard, as such they have disadvantage on saving throws against being frightened unless they have 2 or more allies within 5ft of them.

Squeezable

Much like a cat, a skaven is able to squeeze its way through very tight gaps. They can freely dislocate their shoulders with no ill effect to fit through spaces up to 2ft wide. Moving through a gap such as this quarters their movement speed.