Minecraft wiki entry for Configured_feature, associated text: end_spike
 crystal_invulnerable: (optional) Defaults to false.
 crystal_beam_target: (optional) Block position of the beam target.
: The X coordinate.
: The Y coordinate.
: The Z coordinate.
 spikes:
A spike configuration.
 centerX: (optional) The X coordinate.
 centerZ: (optional) The Z coordinate.
 radius: (optional) The radius of the spike.
 height: (optional) The height of the spike.
 guarded: (optional) Whether to generate a cage around the crystal.