Mastery 2: Deadly.
Mastery 4: +3/+3.
Card sounds may differ from in-game as they get updated.
Deadly - Units and spells with Deadly kill any unit they damage, regardless of health. For example, a 1/1 with Deadly can kill a 5/5 attacker.
Mastery - All damage dealt by units with Mastery count towards its Mastery ability. When its Mastery number is met, it uses its Mastery ability.