Boon of the Ultimate Familiar (5e Epic Boon)

This boon can be awarded to a Warlock with the Pact of the Chain

Your familiar gains the following abilities:

For each level you have your familiar gains an additional hit die and increases its hit points accordingly.
Your familiar has abilities and game statistics determined in part by your level. Your familiar uses your proficiency bonus rather than its own. In addition to the areas where it normally uses its proficiency bonus, a familiar also adds its proficiency bonus to its AC and to its damage rolls.
Whenever you gain the Ability Score Improvement class feature, your familiar abilities also improve. Your familiar can increase one ability score of your choice by 2, or it can increase two ability scores of your choice by 1.
The familiar can now maintain a caster's concentration, allowing the caster to cast a second concentration spell.
The familiar gains the ability to speak and understand Common if it does not already.
Your familiar can be a Medium or smaller creature with a maximum challenge rating of 2.