Christ's first letter to the churches focuses on the Ephesians, a people who succeeded in trying the spirits, but in the interim left [their] first love.
The Ephesus church effectively battled various heresies, for which Christ commends it. However, the members lost sight of the reason, having left their first love.
As High Priest, Christ is putting His people through the paces, tailoring the trials and experiences needed for sanctification and ultimate glorification.
Unity has to come from the inside out, with God raising a leader which His people, having their minds opened by His Spirit, will voluntarily submit to.