Rules overview for Chants of the Old Ones

About Chants for the Old Ones, from BoardGameGeek:

The arrival of the Old Ones is near, we already feel their presence in the air, on the ground in every corner. In Chants for the Old Ones, we will be cultists infiltrating the cities of Arkham, Innsmouth, and Kingsport performing sacrifices, recruiting cultists and summoning creatures to invoke the Old Ones under the watchful eye of seasoned researchers who will try to prevent it. Build the first cult to summon an Old One and start the new era of glory.