The Rexon (ザウラ,Zaura?) is a recurring enemy in the Sonic the Hedgehog series. It is a mass-produced dinosaur-based Badnik created by Dr. Eggman that reside in lava pools and shoot its targets with energy projectiles.
Rexons are Plesiosaur-looking Badniks whose armored carapace can withstand the immense heat of their domain. Their backside (or shell) is indestructible. Their plating is light purple and light grey.
Sonic the Hedgehog 2
In their first appearance in Sonic the Hedgehog 2, Rexons only appear in the lava pools of Hill Top Zone. When the player gets near, the Rexons' head and neck will pop out of the lava and start shooting energy projectiles at the player from one position while their necks stay in motion. However, since the Rexons do not change their heads' direction, it is easy to defeat them from behind using the Spin Jump.
Since their body is invulnerable, the player must attack the Rexons' head. When successfully struck, the Rexons' head and neck will collapse while their main body is left behind to float in the lava pool. Since the playable characters will not take damage from touching the Rexons' main body, the player can use it as a stepping stone in the lava pools for purposes like getting closer to the Rexon's head to beat it.
In Sonic Blast, Rexon-looking Badniks appear in Red Volcano Zone Act 1. These Badniks are red instead of purple and do not appear that often. Similar to the Rexons in Sonic the Hedgehog 2, these Badniks emerge from lava pools and will shoot projectiles at the player when they get close, while steadily moving around in only one position. However, only their heads appear while their main body seemingly remains beneath the lava.
Like the Rexons, these Badniks do not charge the direction of their heads after coming out of the lava, making the easy to defeat. Also, like in every Game Gear/Master System game, these Badniks do not have Animals inside them.
The Rexons retract into their shell until their sensors indicate an enemy presence. When a target is spotte,d their neck and head retracts and floats above the surface. Internal heat mechanisms allow the Rexons to spew dangerous fireballs from their mouths periodically. Despite their intimidating appearance, Sonic found ways to exploit their platform-like shells as a stepping stone to beating them.
In other media
Sonic the Hedgehog Yearbook 1992
The Rexon made a small appearance in Sonic the Hedgehog Yearbook 1992' story "Space-Hedgehog" where it and a Spiker ambushed Sonic the Hedgehog, with Rexon shooting fireballs at him. After beating Robotnik, Sonic defeated both the Rexon and Spiker easily and released the animals inside them.