The Eternia Playset (aka "The Towers of Eternia") is the largest Masters of the Universe toy ever to be produced by Mattel. The playset features 3 towers, a monorail track, and vehicles that run on the track around the entire playset.
Because it is so difficult and expensive to complete, Eternia is commonly referred to as "The Holy Grail" of MOTU collecting. Eternia was originally released at an extremely high price for a toy at the time. This led to few playsets being sold. In addition, there are numerous accessories and other easily lost parts that makes a complete version very hard to put together or find. Many parts, especially the monorail track, are also extremely fragile further decreasing the number of parts available to complete a playset.
The Central Tower is the largest of the three towers. It is approximately 31 inches tall. The central tower has 4 floors - the base or foundation, two mid-levels, and a top level parapet.
The base of the central tower features a moat, drawbridge, and guard lion. The lion's arms move together to capture approaching figures by means of a small lever on the right side of the base. The jaw of the lion can be closed from inside the tower. Closing the jaw allows the drawbridge to drop down inbetween the lion's arms and across the moat, thereby letting a figure enter the tower. There are two gold gargoyles that sit in front of the drawbridge. One of the gargoyle spots is actually hollow (as seen in issue #6 of the Star comic book series http://www.he-man.org/publishing/item.php?id=1497)
Interestingly, most of the weapons that came with Castle Grayskull (and then later with weapons pack) are actually sculpted into the bottom of the moat. In addition, the outline of He-Man's power sword can also be seen! There are also various bones, a series of footprints, and a monster under the drawbridge all sculpted into the moat.
The lower mid-level of the central tower has a computer console mounted on the wall. A command console seat, suspended from the ceiling, allows a figure to sit at the computer.
The upper mid-level has a slot that the top of the command console seat fits through. A gold circular piece of plastic locks the chair in place. The seat can be moved by shifting the circle around. This level is otherwise empty.
The top level of the central tower has space for the red and gray laser blaster cannon. The windshield of this cannon is easily lost. There are 3 gold flag holders that fit the 3 flags.
Each level of the central tower can be reached by an elevator. The elevator can be manually raised and lowered by means of a hand crank at the base of the elevator shaft.
The Grayskull Tower is modeled after Castle Grayskull. Its central feature is a prison and prison gate. To close the prison gate a ball is attached to a chain that runs down to the gate. The chain is placed over a brace on the monorail support and the ball then snaps into place at the end of the support. When a vehicle comes by on the monorail, the ball is knocked free, and the prison gate slams shutting capturing any figure inside the tower.
The Viper Tower is modeled after Snake Mountain. Its central feature is the viper head, which can periscope up from the main tower section. There are 4 chains that run from the monorail supports to the collar around the viper head.
The Monorail System is made up of 13 pieces of monorail track. Eternia comes with 3 vehicles designed to travel on the monorail track. The Power Module is a small battery-powered engine that can connect to any one of the 3 vehicles and power them around the track.
The 3 vehicles are: the Battle Tram (white), the Sky Cage (purple), and the Jet Pack Fighter (gray). The battle tram has a tinted front window. The back of the battle tram opens to allow a figure to fit in. The sky cage also holds a figure. When the red tab on top of the cage is moved in either direction, the bottom of the cage drops out and the figure in the cage falls out.
The monorail track attaches at 5 blue monorail arms on the Central Tower, 4 brown monorail arms on the Grayskull Tower, and 4 gold monorail arms on the Snake Tower.
There are many accessories and weapons included with the Eternia Playset. There is a gold weapons rack, a gold ladder, and 4 silver grappling hooks. The weapons include a silver cross bow, a silver sword, a silver wrench used to hold the lion's job open, a gold bow (identical to Ninjor's bow except for the color), and 2 other laser guns (one gold and one silver). The Grayskull and Snake towers each have a brown ramp. These can lead to the towers themselves, or can be used to connect the towers to Castle Grayskull and Snake Mountain. Lastly, there is a gold manta ray for the moat.
A further reminder - handle the monorail track with care! Track parts have been known to break during assembly even when being put together straight out of a recently opened MIB Eternia. Once assembled, do not try to take the monorail track apart! If your track is assembled, it is probably best to leave it that way. If your track isn't put together, it's probably best not to try to assemble it.