Eldritch Bond. You can add your Proficiency Bonus to any ability check or saving throw that the familiar makes.
Eldritch Strike. Melee Spell Attack: your Spell Attack Modifier to hit, reach 5 ft., one target. Hit: 2 + half your Warlock level (round up) damage of a type determined by the familiar’s creature type: Aberration (Acid), Celestial (Radiant), Dragon (Fire), Fey (Psychic), Fiend (Poison), or Undead (Necrotic).
Invisibility. The familiar has the Invisible condition until the end of its next turn.