Minecraft wiki entry for ED, associated text: Entity data
Tags common to all entities[show]
 BeamTarget: The block location its beam points to.
 X: X-coordinate.
 Y: Y-coordinate.
 Z: Z-coordinate.
 ShowBottom: 1 or 0 (true/false) – if true, the End Crystal shows the bedrock slate underneath. Defaults to false when placing by hand and true using /summon.