You have gained fey companions that take the form of animals and steal for you.   

Find Fey Familiar

Starting at 3rd level, you spend 10 minutes to do a small, magical ritual that summons a fey familiar.   When you do the summoning ritual, your familiar appears in an unoccupied space touching you.  The familiar has the statistics of the chosen form, though it is a fey.   It can take any of the following forms:  Flying Snake, Blood Hawk, Spider, Raven, Octopus, Frog, or Flying Monkey.  It's Intelligence is raised to 8 (if not already higher) and it gains three actions: Detect Traps,  Unlock, and Steal.

As an action you can telepathically command it to Detect Traps and Unlock locks as long as you are within 30 ft of it.    It does so using your own skills.  It knows it can be resummoned upon death, but does not like the experience and you may be within the trap's activation area.  It will sulk and delay (wait 1 turn before obeying commands) if you do not give it a food treat after being resummoned upon death.

As a Bonus Action, you can telepathically direct it to use the steal action against a specific named item.  It can also do so on it's own, but will usually only Steal food or items from your allies (which it knows it won't kill it or get you in trouble).

Steal uses your Sleight of Hand skill and is limited to items weighing less than 10 lbs and not worn.  For purposes of this ability, any thing that the wind could blow off your head is not 'worn'.   If the item is in the possession of someone else, the DC is an opposed check of the Thief's Sleight of Hands vs victim's choice of Animal Handling, Acrobatics, or Intimidation skills.   If the item is in their hand (such as their weapon), they get a +6 bonus to whichever check they choose.  As always, the DM may rule the victim is distracted and has disadvantage, or suspicious and gets advantage.

In addition, if your familiar is trying to steal during the same round you are attacking them, they have a choice to make.  The victim can either accept disadvantage on their Opposed check to stop the attack or you get Advantage on your attack.

Your familiar acts independently of you, but it always obeys your commands.  In combat, it uses your initiative and acts directly after you but on your turn.   The familiar can't attack (yet...), but it can take other actions as normal, including the Steal action above.

When the familiar drops to 0 hit points, it disappears, leaving behind no physical form. It reappears after you repeat this ritual gain. As an action, you can temporarily dismiss the familiar to a pocket dimension.  Alternatively, you can dismiss it forever and repeat the ritual to gain a new familiar of any type.  As an action while it is temporarily dismissed, you can cause it to reappear in any unoccupied space and it is touching you.  Whenever the familiar drops to 0 hit points or disappears into the pocket dimension, it leaves behind in its space anything it was wearing or carrying.

While your familiar is within 100 feet of you, you can communicate with it telepathically. Additionally, as an action, you can see through your familiar's eyes and hear what it hears until the start of your next turn, gaining the benefits of any special senses that the familiar has. During this time, you are deaf and blind with regard to your own senses.

You can't have more than one familiar at a time, including any from spells or other class features such as Pact of the Chain. 

Sneaky Familiar

Starting at 9th level, your familiar can choose to Hide or Dash it's speed as a bonus action.  When it uses it's BA to hide it uses your Stealth skill as  an opposed check against Perception.

While hidden from someone, your familiar gains the following abilities:

• If it hides behind something solid (including you), it gains full cover.  Others may attempt to eliminate this cover if they find it (i.e. opposed Perception check vs your Stealth score).  If they are hiding on your body, they have 1/2 cover even if their opponent made their opposed Perception check.
• While trying to hide on your body it has Fey Evasion:   Against all (not just Dex) saving throws failure means it still only takes half damage and success means no effect at all.  Note, this stacks with the Cover rule above.
• It has advantage on it's next attempt to steal from anyone that failed their opposed perception check and is within 5 ft of their hiding spot.

Violent Famliars

By 13th level your Familiar can now make an attack as an action, if you command it to via a telepathic bonus action on your part.   It uses your to hit and if does normal damage for their animal type + 3d6.  That damage rises to 5d6 when you hit 17th level.    Also, if it attacks someone that you are attacking, it gains advantage on the attack.

Martyr

When you reach 17th level, your familiar is now so loyal it will literally die for you.   If your familiar is within 30 ft of you, when you are about to die from any attack roll (ranged, melee, spell, weapon, as long as it has a to hit),  your familiar will spend it's reaction to take the blow.   It teleports the 30 ft and is hit instead of you.   You take no damage from that attack, and it dies if the damage exceeds it's current hit points.

In true Comic book fashion,  death is only temporary.  The ritual can be used to return it. but if this ability caused it's death,  the ritual expands from 10 minutes to 1 hour of begging and offering 1,000 gp worth of high end foods, regardless of whether you are getting the old familiar or a new one.  (You cannot get any of the benefits of a short rest if you use this ritual, unless you spend another hour resting).

In addition, this ability cannot be used again until you take a long rest.

P.S.  At this level your familiar's damage rises, as mentioned earlier in Violent Familiar