The Church of the End is one of the three religions in the Realm of Vasten. You might find churches built in many of the villages, towns and cities across the realm. Most have something believers call a Leap of Faith. It is how the church sacrifices people to their god, the Ender Dragon. The put the believer on the glass at the front of the church and that person believes in the Ender Dragon as hard as they can. When they are ready, as the sun sets, they push the button, opening the glass and dropping them into lava. The best believers believe they will be teleported to the end to be devoured by the Ender Dragon.
The Church's capital can be found just west of Kelael, in a swamp. It is a majestic building raising some 250 blocks above the swamp and is built directly above an end portal.
Every church Leap of Faith will teleport you to the End Temple, where you can drop into the End Portal and repair tools in the Ender Ender.