You have made a pact with the spirit of a familiar. A being from the astral plane normally of service to spellcasters that desires more than to be just a servant. Whatever its reason may be, whether it wants to be free from its master, become more powerful, or simply wants to see what it’s like in the material plane, it has made a pact with you to share its magic. 

Level 3: Eldritch Familiar

Starting at third level whenever you cast the Find Familiar spell, you can summon your patron as an Eldritch Familiar instead of the creature you would normally summon. Familiars summoned by the find familiar spell take their turn after yours in combat. When you first gain this ability, or level up you use a pool of 15 points to spend in the table of traits, abilities, and stat buffs below for your Eldritch Familiar. (see my Eldritch Familiar monster for base stat block.)

1:Talons, melee attack :+your Charisma modifier :1D8 slashing damage +your Charisma modifier

1:Fangs, melee attack :+your Charisma modifier :1D8 piercing damage +your Charisma modifier

1:hamer, melee attack :+your Charisma modifier :1D8 bludgeoning damage +your Charisma modifier.

2:Fins, +30 ft swim speed.

2:Quills, ranged attack , range 30ft: +your Charisma modifier: 1D6 piercing +your Charisma modifier.

3:Hide, +3 AC.

3:+2 initiative.

4:+80ft Darkvision

4:Venom, melee attacks deal an extra 1D4 poison damage.

5:+10ft speed

5:+20ft fly

6:+melee attack: +your Charisma modifier :1D6 bludgeoning, on a successful hit, the attacked creature must make a strength saving throw against your spell save DC. on a failed save the creature is knocked back 30ft.

Level 6: Karma Companion

Starting at 6th level, your Eldritch Familiar has grown a close bond with you and your friends. when you or a friendly creature takes damage from a creature within 5 feet of your Eldritch Familiar. You can use your reaction to cast a damaging cantrip from your Eldritch Familiar targeting the creature that attacked.

Level 10: Magical Metamorphosis

Starting at 10th level. Because of the experiences you and your patron have gone through. Your patron gains an influx of magic from the astral plane and grows into a stronger form. You can change its size between small to large as a bonus action , and you can choose 2 more abilities from the Eldritch Familiar table for your patron. When you first gain this ability or after a short or long rest, you can choose 2 additional abilities from the table below for your Eldritch Familiar.

Dark infusion. The Talons, Fangs, and Hammer attacks become coated in magic, they are treated as magic weapon attacks, and deal an extra 3D8 Necrotic damage.

Breath Weapon. As your Eldritch Familiar's action, Spend one of your spell slots. Creatures within a 30 feet cone or 60 feet line from your Eldritch Familiar must make a Dexterity saving throw. On a failed save, creatures in the area take 8D8 Fire, Poison, Lightning, Acid, or Cold damage. On a successful save, they take half that amount.

Magical Exchange. As your Eldritch Familiars Bonus action. It can lose 40 hit points, and you regain 1 of your expended spell slots.

Enhanced Mobility. Your Eldritch familiar grows various limbs for movement. It gains + walk 30ft, + swim 30ft, + fly 60ft, + climb 30 ft.

Resculpt Body. Your Eldritch familiar’s magical  body allows it to cast Polymorph on itself a number of times a day equal to your Charisma modifier as if you casted it. It can turn into a copy of you without any class abilities this way.

Level 14: Better Together

Starting at 14th level, your bond with your patron has grown to a point of ultimate trust. Once per long rest, as your action, or your Eldritch Familiars action, you combine with your Eldritch Familiar into one creature for the next hour. While in this state, you gain all benefits and abilities your Eldritch Familiar would gain from your Eldritch Familiar and Magical Metamorphosis class abilities, your size becomes Huge, and your creature type is monstrosity. When you use this ability you can choose one of the following abilities to gain while you and your Eldritch Familiar remain combined.

Magical Surge. You can cast leveled spells a number of times equal to your Charisma modifier without expending a spell slot.

Aura of Misfortune. When a hostile creature within 15 feet of you is attacked, that attack has advantage. And if the attack is a critical hit, it deals an extra 4D12 Necrotic damage.

Constraining Pseudopod. As an action, you can extend a tentacle-like limb from your shifting body and attempt to grapple a creature within 30 feet of you. The creature can make a strength saving throw against your spell save DC on a failed save, the creature is grappled by you and if its size is medium or smaller it is considered to be carried by you. You can only carry up to 5 creatures at a time this way. At the start of a grappled creature's turn they can make a strength saving throw against your spell save DC, on a successful save they escape your grasp and are no longer grappled.

Marked Retribution. After you hit a creature with a melee weapon attack, that creature must make a wisdom saving throw against your spell save DC. on a failed save, that creature is marked until the end of your next turn. If a marked creature attacks another friendly creature, the next attack you make on that creature is a critical hit and deals an extra 3D12 Necrotic damage as long as the creature remains marked.