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STN-9O Sentinel
Custom Design
Designer Mortarion12
Production information
Manufacturer Eisen Unlimited
Model Sentinel
Class Medium
Technical specifications
Mass 40 tons
Chassis EisenOct Omni/ES
Armor StarShield Light
Engine 240 Krieg Light
Speed 97.8km\h
Jump Jets None


BV (1.0) ???
BV (2.0) ???


Widely regarded as an antiquated design, the venerable STN-3L Sentinel served the original Star League well. The concept behind this was battalion-level ‘Mech support for infantry formations. Due to the exhausting decimation of the Successor States during the wars, the STN-3L was reduced to a few hundred examples. This was mainly because in stand-up BattleMech fights, other designs had either an edge in firepower or in speed. Therefore by the time the 3050’s rolled around, the Sentinel was not on many engineers mind…Except for EisenUnlimited. EisenUnlimited has been so far a shadow company, cropping up some time in early 3015. They primary factory is a closely guarded secret due to fear of losing the only asset keeping them in business. Surprisingly they mainly operate right over the border of the Lyran Alliance. They currently maintain three production lines; one medium, and two heavies. Curiously specializing in Star League designs, EU has taken out part-contracts with Defiance to facilitate the implementation of OmniMech refits of Star League ‘Mechs. The STN-9O is the first of these refits, built-to-order straight from EU, the STN-9O is a capable and versatile fighter on-par with even some clan 'Mechs.


The designers at EU took the original weapons load out of the STN-3L and asking what they could improve. The Kawabata Ultra A\C5 located in the left arm had long been the big gun of the Sentinel. EU realized that although the damage output was respectable, it’s range was limited and the Ultra series have a tendency to jam. The primary configuration replaces the U A\C5 with a Zeus Slingshot Light Gauss Rifle. This increased reliable damage and range out to an astounding 750 meters. With a primary gun selected, EU then turned to close-in weapons. The original STN-3L used a Streak SRM-2 and Small Laser when targets got into minimum range of the A\C. Thanks to new materials, EU turned this weapons combo into a deadlier mix. The weight saved by a Light Fusion allows the Streak SRM-2 to be upgraded to a streak quad-rack and one ton of ammo. The small laser is replaced with a powerful extended-range medium version. This primary configuration has proven to be a good mix of long-distance hitting power, and guerrilla-style close combat with other light mediums. All this is mounted to 40 ton custom-built Endo-Steel chassis mounting 6.5 tons of Defiance StarShield Light armor. Backed up by an XL Gyro and double heat sinks, the STN-9O can carry an incredibly diverse set of weapons.


The Alt. A configuration is an urban brawler with a short heat curve. The light gauss is swapped out for a Blankenburg Large Pulse Laser. The short-range weapons are also changed to two Tronel XII Medium Pulse Lasers. The radical changes are the addition of 6 Rawlings 55 Jump Jets and a Hatchet built into the Right Arm shaped like a short sword.

Alt. B changes the ‘Mech into a dedicated sniper platform. The big gun is changed to an AberDovey Mark XXX ER PPC. The missile bay is upgraded to a Holly 10 LRM-rack linked to an Artemis IV system and two tons of ammunition. Close Range defense weapons are removed to add an ECM bank and a McArthur II Anti-Missile System. Ammo Bays are protected by a CASE system as well.

Alt. C was designed for endurance. Using the idea from the original Banshee but on a smaller scale, EU loaded this out for medium range fire support for other ‘Mechs. A Mydron SnakeKiller Light A\C5 is the main gun, with two tons of ammo in a CASE system. Added to this is one Magna Mk VI ER Medium Laser in the Right Torso. The advanced firepower comes from two Blankenburg Light PPC’s. One is placed in the Left Torso and one in the right.

Alt. D is the final official variant. This is a bruiser version. A large Defiance Disintegrator LB10-X Autocannon is placed in the Left Arm. Backed up by CASE and two tons of ammunition; this variant has some staying power. The Coup de Grace is the 4 Magna Mk VI ER Medium Lasers spread through the two side torsos.