From publisher blurb:
Meet your life-long friend that will stick with you through thick and thin. The summoner class allows you to start off with a companion and when that isn’t enough, you gain the power to summon other allies to suit your needs of the moment. Over time, your power and the powers of your companion grow over time, and the two of you make an unassailable pair and you eventually reach a point where the two of you become one.
Designed for the 5th edition ruleset, the Summoner class offers a bonded companion at 1st level along with spellcasting abilities. Upon reaching 2nd level the summoner gains the ability to conjure others creatures from the ether. As the summoner increases in level, her companion gains new abilities and the creatures from which the summoner may conjure become more fearsome. And eventually the summoner gains the ability to infuse her companion with herself and learns to summon other creatures for indefinite periods of time.