Reptilicus

The Reptilicus are creatures from Metroid Prime 3: Corruption. They are apparently the savage, devolved remnants of the once great Bryyonians.

Description
A Reptilicus can be distinguished from a Reptilicus Hunter by its generally darker coloring, as well as the spiny protrusions located on its back, similar in appearance to the flora on Bryyo. They are large, lizard like creatures with six limbs, standing on their back two legs when wishing to attack and for intimidation. They appear to wear a skull-like mask on their faces.

They use highly advanced technology despite their feral appearance; they have the ability to teleport and use high-tech weapons, including an electrical whip-like weapon, some form of boomerang and a projectile weapon, possibly arcane. They are resistant to Fuel Gel but weak to extreme cold, so it is possible that they originate from one of the warmer regions of the planet. Likely because of their strong affinity with Fuel Gel, they are immune to the burning effect of the Plasma Beam, but can still be killed if they fall into Fuel Gel. Reptilicus also use Warp Hounds for assistance, creatures that have been trained to ambush enemies, and that share the teleporting ability of the Reptilicus. Warp Hounds are most often used by Reptilicus Hunters over the standard Reptilicus, showing that the Hounds are used for hunting purposes as well as guarding.

Attacks
In terms of weaponry, the Reptilicus are dangerous opponents. At close range they will make a sweeping strike with an energy whip, distorting the visor temporarily.

At longer distances the Reptilicus make use of the chakram they wear rather ornamentally around the neck. Samus knows when it wishes to strike as the creature can be heard drawing this throwing weapon. This attack can be avoided by a side dash, or by jumping over the chakram at the right time. They can also create a glowing sphere out of magic and strike Samus with it if she is very close to them. What really makes the Reptilicus stand out though is its ability to teleport, allowing it to close short distances with its enemies. They will do this if Samus is too far away to attack and can also sneak behind her this way. However, the sound and light produced when the Reptilicus teleports and reappears usually give away their presence.

Reptilicus often teleport extremely close behind their enemies, to ambush them. They seem to teleport to fixed positions on the battlefield as well. Reptilicus can leap great distances unaided, suggesting they have powerful leg muscles. However, they occasionally miscalculate a jump across a pit and fall to their doom. Unlike Warp Hounds though, they only teleport to move in to attack and do not usually use it to escape or dodge, which means that they can be targeted more efficiently than Warp Hounds. Until Samus finds the Ice Missile, Reptilicus can be tough opponents to defeat, especially in large numbers. It is probable that when the Plasma Beam is acquired, the shots are weaker due to that their bodies are heated. However, they are not as strong as Reptilicus Hunters. On the other hand, due to their extremely efficient close-range attacks, they are best engaged from a distance.

Devolution
There's some debate as to how they became vicious monsters and immune to Fuel Gel. The Bryyo Lore mentions it's because they were unable to merge magic with science, and thus started a feud. On the other hand, the log entries for Reptilicus Hunters and Reptilicus hints that their savage nature and immunity to Fuel Gel is a result of Phazon from the Leviathan, since it says that their higher thought processes have been degraded by Phazon, although that has given them their ability to teleport, implying that they still had some sort of culture and thought after the feud (possibly supported in that they still know how to make and use plasma whips and their signature chakram), but lost it after the Leviathan corrupted them.

Matt Manchester's notes on the Armor suits
"These displays of ceremonial armor were fun to make. I was hoping to imply more culture and ceremony than what was there in front of you, to hopefully get the player into imagining how the Bryyo society might have functioned."

Trivia

 * The electric whip used by the Reptilicus may have been based on the Plasma Whip, an ability of Samus' Paralyzer demonstrated in Super Smash Bros. Brawl, or a weapon of the same name that made its debut in the third Ratchet and Clank game.
 * If Samus completely freezes one after it throws a chakram, the chakram, when it heads back to its owner, will hit the Reptilicus causing the Reptilicus to shatter and die. This is called "Icy Reptilicide", and the player gains a Friend Voucher for it.
 * Two Reptilicus skeletons are found imprisoned near the Warp Site to Bryyo Ice from Bryyo Fire. One of them died trying to escape, breaking its neck in the process.
 * In one room in Bryyo Fire, several suits of armor decorate the walls. These suits were made to fit Reptilicus, indicating that the Bryyonians had an army at some point. These suits also feature the chakram used by the modern Reptilicus. Also they glow a soft orangey yellow, implying they may be forged from Crystallized Fuel Gel. This would appear to make sense, as in one room, crystallized Fuel Gel can only be destroyed by igniting other nearby old and weaker crystals, showing how resiliant it is.
 * The species may have been named after the 1961 monster film Reptilicus.