Jaernadon are Scourgan enemies found in the End. They are ghostlike mobs that can fly through blocks. They have no legs and appear to be wearing chain armour and a diamond axe. Their name in Scourgis means "Dragon Herder".
Hence their name, Jaernadon can summon dragons and scoot them over towards players with their axe without actually hitting them. Dragons around Jaernadon fly somewhat faster. These Dragon Herders are ghosts and need a Spirit Scythe in order to kill. They use their axe to attack players. They drop Skeleton Skulls upon death.
Jaernadon live in the End, usually one spawning every time there is a dragon spawned. Sometimes more dragons come when a Jaernadon is nearby.