In Revelation 2:18-29, Jesus sent the longest letter to the church in the least important city, Thyatira, perhaps because its situation was complicated.  In general, it was a great church, growing in faith and love.  However, they tolerated false teaching that led to bad living.  Jesus himself would deal with the false teacher and her followers, and he called the rest simply to hold on and keep going until the end.  This letter summarizes the message of the whole book of Revelation: Jesus has conquered and will conquer, so we need to keep living in faith and love in order to conquer and reign with him.