- You may be looking for Rexxon.
Rexon (ザウラ Zaura?) is dinosaur-type Badnik created by Doctor Robotnik, that has made first appearance in Sonic the Hedgehog 2. Rexons are plesiosaur-looking Badniks, which are seen in the middle of lava pools to shoot its target down with energy projectiles.
Sonic the Hedgehog 2
In its first appearance of Sonic the Hedgehog 2, Rexons are only seen at many lava pools of Hill Top Zone. Rexon's head first pop out the lava and starts shooting energy projectiles to the player at one position while its neck keeps moving. However as these Badniks doesn't move its head direction, it can be surprisingly easy to defeat behind by using Spin Jump to attack its head or leave to the one place and move on.
As the player defeats the Badnik, its head and neck collapse while only leaving its main body to float in the lava pool, which doesn't do any damage by touching it.
Sonic BlastRed Volcano Zone in Sonic Blast. These Badniks are red colored instead of purple and don't appear that often, as only being featured at first act of the zone. Similar to Rexon in Sonic the Hedgehog 2, it only keeps moving at one position after coming out the lava pool while it starts shooting small projectiles.
However once again, these Badniks also don't turn its direction after coming out the lava, as the Badnik can be easily defeated. This Badnik also doesn't seen to have main body floating in the lava and like in every Game Gear / Master System title, these Badniks also don't have Animals inside them.
Sonic Rivals 2
A Rexon resides in molten hot lava, its armored carapace meant to withstand the immense heat of its domain. Its backside (or shell) is indestructible and can be used as a platform, but when an enemy comes near, the head and neck retract from their safe home to spot intruders. Their necks are not 100% stable, so it sways back and forth while they search around. Their plating is light purple and pale blue. The appearance of this Badnik is based on plesiosaurs, according to pictures in the game manuals. When they are destroyed the head and neck detach and are destroyed, leaving only the shell behind.
The Rexon retracts into its shell until its sensors indicate an enemy presence. When a target is spotted their neck and head retracts and floats above the surface. Internal heat mechanisms then allow the Rexon 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
Rexon has made small appearance in Sonic the Hedgehog Yearbook 1992' story "Space-Hedgehog" as one of two Badniks with Spiker to threat Sonic the Hedgehog and is shooting fireballs to him. After Sonic getting frozed and sent with space rocket to the space, he gets out from the space rocket and beats Robotnik. He then defeats both Rexon and Spiker easily, thus releasing animals on them.
Sonic the Comic
In the Sonic the Comic series published by Fleetway Editions, the Balkeries are a part of Dr. Robotnik's Badnik army. They only appeared in Hill Top Zone where they ran Robotnik's operations from lava pools. Unlike most other Badniks in the comics, the Rexons retained a consistent design over the series' run.
- Rexon's mechanical fins are never seen in gameplay due the Badnik being residing in lava pools where only its head, neck and main body are visible.
- In Sonic the Hedgehog Spinball, a similar but larger robot named Rexxon appears in the Toxic Caves, which would be somewhat successor of Rexon by comparison of name and appearance.
- Rexon is seen on one of the winning fan arts in Sonic and the Black Knight.