The Secret of the Yetzer Tov / Good Inclination

Synopsis is not necesarrily in Rabbi Kessin's own words

Everybody knows that Evil Inclination, or Yetzer HaRah, or Satan, or Malach Hamaves, is an angel assigned to do the job.

We’ve also heard about Good Inclination, or Yetzer Tov.

However, the nature of Yetzer Tov is obscure. Somehow nobody heard about an angel representing Good Inclination. What is it, really? What kind of a creature, what kind of a being is hiding behind the term?