Obsidian is one of the figures in the second run of Beast Machines basics. Adding another Vehicon to the fray in such a small size is great and it's a cool toy too!
In vehicle mode, Obsidian is a vertical take off/landing vehicle. He is mostly bright green with dark blue patterns. Bright orange is used on his missiles while translucent orange is used for his rear tail fins, rotors and cockpit. The rear of the vehicle and the rotor engine sections are a darker shade of green. Most of the green parts on Obsidian have a metallic "flake"pattern giving it a slightly metallic look in the right lighting conditions.
Obsidian's design is very nicely done. The cluster of missiles on either side are reminiscent of missile launchers from most anime mecha robots. The wings are nice and angular with subtle details such as vents. Like his fellow flying Vehicon, Jetstorm, Obsidian has a pattern on his cockpit which resembles eyes staring down at his enemies. Obsidian does have landing gear in the rear which can fold down. The wheels do not turn however.
In vehicle mode, Obsidian can turn his rotors so they face forwards, making him look more like a plane than a VTOL. The rotors can be launched by pressing the back of each rotor piece. Spring loaded firing mechanisms would have been preferable. Also, a small gun mounted under the cockpit can move up and down. A cool vehicle mode.
Transformation to Robot Mode:
Begin Obsidian's transformation be separating the halves of the rear of the vehicle. Fold down the landing gear to form the robot legs and feet. Next, fold down the cockpit and then the robot head. Now swing the missile launcher sections out to the sides a bit and fold them down to form the robot arms. Obsidian is now in robot mode!
In robot mode, Obsidian is one mean looking robot. His colors are primarily the same, but the dark green on his legs and rotor engine sections is much more prominent. His robot mode head uses the same blue, bright green and bright orange that is on the rest of his form. His detailing is cool, and his face goes along with the style of robot heads used with Thrust and Jetstorm. Although he doesn't have hands, the fact that both his lower arms end in multi-missile launchers is pretty cool.
As a robot, Obsidian has thirteen points of articulation. His rotors can be aimed forward, just like in vehicle mode and fire at his enemies. Obsidian's primary fault is similar to Longhorn's. In robot mode, there is a huge gap between his robot head and the cockpit piece, which is meant to form his chest. One can lower the robot head so that it is right on top of the cockpit piece, but then he looks like someone hit his head so hard it got stuck in position.
Although not an "official" transformation, you can keep Obsidian's two legs together and then angle them to resemble the television show's "hover mode". Unlike Jetstorm who has a hover mode described in his instructions, Obsidian's is not. The mode does look nice however, and the picture in this review of that mode has the cockpit piece snapped off to greater resemble the television show character. However, I do not recommend persistent snapping off of parts.
Overall, Obsidian is a cool toy, and a worthy addition to any Vehicon army. He may have a flaw or two, but it doesn't subtract from the fun of the toy too much. B+
Updated Thoughts (March 22, 2022):
As I looked at my old review above I was surprised to find I only gave this figure a "B+". The Basic Class went away a long time ago (sort of replaced by the Scout Class later, which itself is long gone in 2022) and I find myself really missing figures that are not huge, but have good, solid transformations and neat alt-modes. Obsidian definitely qualifies as one such figure. His transform is fun but easy. His detailing is fantastic and he has a very different robot mode aesthetic than your typical humanoid looking Transformers figure. Nowadays I would definitely give this guy an "A" and I am kind of sad that we never got the rumored larger version of Obsidian back in the day.