This article is about the BattleMech design. For the follow-up design and other uses, see Stalker II and Stalker (disambiguation).
Production information
Manufacturer Defiance Industries[1]

Irian BattleMechs Unlimited[2]

Trellshire Heavy Industries[2]

Triad Technologies[2]

Production Year 2594[3][4]
Model STK-3F[2]
Class Assault
Cost 7,463,825 C-bills
Technical specifications
'Mech type Inner Sphere BattleMech
Mass 85 tons
Chassis Titan H1
Armor Valiant Lamellor
Engine Strand 255
Communications System Cronol PR
Targeting Tracking System Spar 3c Tight Band
Heat Sinks 20 single
Speed 54 km/h
BV (1.0) 1,152
BV (2.0) 1,559[2][4]

Relatively common as assault 'Mechs go, the 85-ton Stalker has been a staple of assault 'Mech formations for centuries. Notably, there is at least one downgrade (implicitly also various field refits) that reduces its mass and turns it into not an underweight 85-ton assault 'Mech but a 70- or 75-ton heavy 'Mech; see Variants and Notes below.


It's not flashy. It's not the cutting edge. It just keeps coming.
-From Triad Technologies marketing campaign[4]


The Stalker was first produced in 2594 as a heavy assault BattleMech for the Reunification War. The engineers and designers at Triad Technologies created the Stalker to be a heavily-armored weapons platform capable of handling combat at any range and absorbing a tremendous amount of punishment. Although among the slowest 'Mechs ever built, the Stalker was still fast enough to keep up with other assault 'Mechs and lead major advances, using its firepower to blast holes in the enemy's lines. Its heavy armor and armament also makes it well-suited for urban combat. Indeed a favorite tactic developed by Stalker pilots was to lie in wait inside a building until an enemy 'Mech passed by, then crash through the wall and emerge onto the street behind them.[3][4]

For nearly two hundred years, the Stalker remained in service for the Star League Defense Force as a workhorse assault 'Mech. After the fall of the Star League it continued in the same capacity for another two hundred years in service to the Successor States. Additionally, though Triad Technologies was destroyed in the Succession Wars, the Stalker remained in continuous production since both Irian BattleMechs Unlimited and Trellshire Heavy Industries began producing the Mech at their factories on Shiro III and Twycross respectively. Both the Free Worlds League and Lyran Commonwealth were thus able to maintain the largest number of Stalkers in their arsenals. Even so, the 'Mech was so common throughout both the Inner Sphere and the Periphery that some pilots lost their fear of it (at least until they had to face one in combat).

Its long career also led to a large number of variants, one of the most common being one which removes ten to fifteen tons of weaponry in order to lighten the strain on its increasingly older, battle-worn skeleton.[3][4] This created at least one subvariant that effectively rebuilds the Stalker as a 75-ton 'Mech. (See Notes below.)

Starting in the late 3040s, Irian began utilizing newly-recovered lost technology to update the original design, improving its weaponry, armor, and heat management capabilities. These new STK-5M models were fielded in time to take part in the Clan Invasion, although even with their upgrades they were severely tested by the Clans' OmniMechs. The Federated Commonwealth also produced their own variant, the STK-5S, although this was introduced towards the end of the invasion. New variants would continue to be produced in the wake of the FedCom Civil War, one for both of the split nations, and by Irian in an effort to further keep the design alive.[5]

Weapons and Equipment[edit]

The Stalker's weapons array is geared to increase damage as it closes with its target. The Stalker's long range weapons are two Jackson B5c LRM-10 launchers, one of each mounted in either "arm" with an accompanying one ton of reloads. These provide the Stalker with its longest-range punch and allow it to give indirect fire support when needed. At shorter range the Stalker next brings its two Magna Mk III Large Lasers split between left and right torsos to bear on its target. For close ranges, the Stalker carries four Magna Mk II medium lasers split between the two arms and two Thunderstroke SRM-6 launchers, each fed by two tons of reloads, split between left and right torso.[3][4]

The number of weapons carried by the Stalker is so great that should a pilot attempt to fire them all at once they would easily overload the twenty heat sinks the 'Mech carries. Originally, the Stalker used a special fire-control computer which determined the range to the enemy and suggested the optimal mix of weapons to avoid such a problem. Inherent to the ravages of age, many older 'Mechs lack this piece of equipment. By the late Succession Wars era, a functional Spar 3c Tight Band targeting & tracking system was considered very valuable.[6] These pilots therefore must take care when in combat: thirteen and a half tons of armor may defend against the enemy's blows, but will do nothing to prevent an ammunition cook-off caused by overheating.[3][4]


  • Downgrades 
    Stalkers suffered structural weakness symptomatic of the extreme stress the 85-ton 'Mech's skeleton had to bear. In later times, this necessitated the lightening of the load by a full ten to fifteen tons. A common solution to this problem was to simply remove the twin LRM-10s, leaving the close-range firepower intact, in order to keep an otherwise capable 'Mech in service. A similar downgrade was to remove one LRM and a laser or two instead.[7][8]
    In some cases, it seems the mass of the internal structure was reduced in those downgrades, creating 70-ton or 75-ton variants. However, official record sheets for 70-ton Stalker variants from Record Sheets Volume Four: Assault 'Mechs described as the STK-4N and STK-4P were since replaced by newer canonical record sheets for these variants from Record Sheets: 3039 Unabridged, leaving only the STK-4P as an underweight Stalker variant with a known alphanumerical code in canon. It remains unclear if other 70- or 75-ton downgrades canonically exist, as construction rules have changed since the publication of Record Sheets Volume Four: Assault 'Mechs and now do allow for 'Mechs to be underweight.
  • STK-3H 
    The -3H variant of the Stalker was introduced by Triad Technologies in 2638 to take part in sieges. The 'Mech removes both large lasers and LRM-10s and replaces them with two LRM-20 launchers and two tons of reloads. This makes the 3H a powerful long range fire support 'Mech.[2] BV (1.0) = 1,249, BV (2.0) = 1,624[4]
  • STK-4N 
    A modification of the Stalker introduced in 2876 which sought to increase its heat efficiency, the -4N model removes one of the LRM-10 launchers and adds six heat sinks to the design. These make the Stalker more heat efficient but also make the 'Mech weaker when engaging an enemy at long range. BV (1.0) = 1,225, BV (2.0) = 1,558[4] (Note: Record Sheets Volume Four: Assault 'Mechs provided a record sheet for an STK-4N variant that was statted as a 70-ton 'Mech, but this was since superseded in Record Sheets: 3039 Unabridged where it is depicted as an 85-ton 'Mech as described here.)
  • STK-4P 
    One standardized downgrade formally identified as STK-4P in 2998[12] reduces the chassis to 75 tons and the armor to 13.5 tons, and removes the left LRM-10.[13] BV (1.0) = 1,126, BV (2.0) = 1,461[13]
    (Note that the STK-4P designation denotes a variant that is constructed as a 75-ton 'Mech, as opposed to an underweight 85-ton 'Mech; see Notes below. Context and construction rules suggest that this is a downgrade that involves the removal of one ton of internal structure and swapping the now-oversized 255-rated fusion engine for a nominally lighter and less powerful one with a 225 rating. It is further implied that the rebuild is a field-refit level downgrade in the case of the Stalker and not the factory-level refit normally required for a change of this magnitude; apparently, the Stalker's Titan H1 chassis is strained as an 8.5 ton internal structure for an 85-ton 'Mech but can somehow be downscaled easily to a stable 7.5 ton internal structure for a 75-ton 'Mech, without requiring a full refit.)
  • STK-5M 
    An upgrade originating from the Free Worlds League, the 5M variant of the Stalker was introduced in 3050 using moderate amounts of Star League technology. Most of the weaponry was retained but both large lasers were removed for a single Diverse Optics Sunbeam ER Large Laser placed in the 'Mech's centerline and an Octagon Missile Magnet Narc Missile Beacon in the left torso accompanied by two tons of reloads, allowing the Stalker to tag enemy units with homing beacon and direct friendly missile fire onto them. The seventeen double heat sinks of the 5M afford it far greater heat efficiency than the twenty single heat sinks of previous models, although it still could not handle firing all of its weaponry simultaneously, and an additional ton of armor was added for survivability. Other changes included the use of proprietary components such as an Irian E.A.R. communications system, Riese-456 armor and an Irian Chassis Class 30. Unfortunately the designers of the new 5M dismissed the inclusion of CASE, a factor which led directly to the deaths of several Stalkers during the Clan Invasion due to ammunition cook-offs caused by overheating and weapon penetrations. BV (1.0) = 1,316, BV (2.0) = 1,655[5]
  • STK-5S 
    Outfitted with the relatively recently rediscovered Star League technology of circa 3050, the FedCom 5S can be characterized primarily by its tendency to overheat. The designers behind this variant took the simple expedient of upgrading its engine and firepower without taking heat buildup into consideration. The 'Mech has had its engine replaced with an XL engine and the large lasers have been removed and replaced with two Thunderbolt-12 Large Pulse Lasers. For protection against ammunition explosions, CASE has been added to both side torsos and an Deprus Swarmshot anti-missile system has been added for protection against incoming missiles. BV (1.0) = 1,009, BV (2.0) = 1,423[14]
  • STK-6M 
    Irian’s attempt to make up for the shortcomings of the 5M, the 6M introduced in 3062 drops the SRMs and Narc entirely, upgrades the LRMs to 15-tube racks with integral Artemis IV FCS and three tons of reloads each, and upgrades the lasers to ER versions, mounting a fifth medium. Most importantly, the LRM magazines are now protected with CASE. BV (1.0) = ?, BV (2.0) = 2,029[14]
  • STK-7D 
    The 7D Stalker introduced by the Federated Suns in 3062 is built on a standard chassis and engine for rugged durability and carries a primarily energy arsenal. Its two primary weapons are two ER PPCs, giving the 7D a striking distance out to just under seven hundred meters. The 'Mech is also armed with four Medium Pulse Lasers for close combat, which are backed up by two Streak SRM-4 launchers to take advantage of any weak points in an enemy's armor. The lasers and ER PPCs are all linked to an advanced Targeting Computer, which gives the 7D extreme accuracy. BV (1.0) = 1,533[15], BV (2.0) = 1,901[14]
  • STK-9F 
    After consumer feedback highlighted several issues with the new Stalker II from Irian BattleMechs Unlimited, IBMU introduced the 9F configuration for the 'classic' Stalker. Largely a Clan-tech retrofit of the STK-3F, the 9F upgrades the 3F's LRM-10 and SRM-6 launchers to Clan specifications and replaces the torso-mounted Large Lasers with Large Pulse Lasers. The arm-mounted medium lasers, however, remain unchanged. The 9F also sports a Targeting Computer and Active Probe system, as well as a Light Fusion Engine, CASE II protection, Endo Steel,and like the Stalker II the 'Mech is protected by Hardened Armor. A modest 13 double heat sinks struggle to mitigate the 9F's heat output.[18]

Custom Variants[edit]

  • STK-3F Stalker Jagawen 
    Designed for close combat, the Stalker used by Sho-sho Jagawen Torisobo in 3028 replaced the LRM launchers with an additional SRM-6 rack in each torso. Six additional heat sinks kept the machine cool. BV (2.0) = 1,570[19]
  • STK-3F Stalker Jamison 
    This variant is the personal 'Mech of J. Elliot Jamison, commander of Wolf's Dragoons' Zeta Battalion, and was built in 3054 as a Clan-tech version of the venerable STK-3F. The Large Lasers were replaced with Large Pulse Lasers, the medium lasers upgraded to ER medium lasers, and a pair of LRM-20s are used instead of the original's ten-tube launchers. Rounding out the weapons array, two ammo-efficient Streak SRM-6s are used. Eighteen Clan-spec double heat sinks are mounted to help control the heat load. Finally, ferro-fibrous armor is used to protect this dangerous BattleMech. BV (2.0) = 2707[20]

Apocryphal Variants[edit]

Apocryphal Content Starts

The information after this notice comes from apocryphal sources; the canonicity of such information is uncertain.
Please view the reference page for information regarding their canonicity.

From MechWarrior Online:

  • STK-M Misery 
    Implied to be a Stalker piloted by J. Elliot Jamison, the Misery Hero 'Mech retains the STK-3F's twin medium lasers in each arm, right torso mounted SRM-6 and center torso mounted Large Laser but removes the remaining SRM-6 and LRM-10s to mount a mammoth Gauss rifle in the left torso. Carrying two tons each of Gauss rounds and SRM missiles, twenty-two single heat sinks strive to keep Misery in the thick of combat.[1]

Apocryphal Content Ends

Design Quirks[edit]

The Stalker has the following Design Quirks:[21]

Related Designs[edit]


  • While reducing the loadout by 10 to 15 tons would typically result in an underweight 'Mech with a nominal 85-ton chassis that is otherwise considered an 85-ton 'Mech under game rules, this is notably not the case for the STK-4P variant which is essentially a new, different 'Mech built on a 75-ton chassis with a correspondingly smaller engine and lighter internal structure. This would normally be considered a distinct 'Mech design, but that does not seem to be the case with the Stalker. (Another example would be the 15-ton variant of the 20-ton Flea.)
  • In German products, the unit's proper name was translated to Pirscher. The model code was accordingly changed to PRS-3F.
  • In French products, the unit's proper name was translated as Intrépide, which means intrepid.



  1. Objectives: Lyran Alliance, p.12
  2. 2.0 2.1 2.2 2.3 2.4 2.5 Technical Readout: Succession Wars, pp. 166–167: "STK-3F Stalker"
  3. 3.0 3.1 3.2 3.3 3.4 Technical Readout: 3025 Revised, p. 110-111
  4. 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 Technical Readout: 3039, p. 162-163
  5. 5.0 5.1 Technical Readout: 3050 Upgrade, p. 98-99
  6. BattleTechnology: The Lost Issues, p. 68
  7. Technical Readout: 3025, p. 116
  8. Technical Readout: 3025 Revised, p. 110
  9. Record Sheets: Operation Klondike, p. 51
  10. Historical: Operation Klondike, p.160
  11. Era Report: 2750, p. 129
  12. Introduction date of STK-4P as per Master Unit List
  13. 13.0 13.1 Record Sheets: 3039 Unabridged, p. 259
  14. 14.0 14.1 14.2 14.3 Master Unit List: Battle Values, p. 152
  15. Record Sheets: Upgrades, p. 140
  16. Record Sheets: 3085 Unabridged — Old is the New New, p. 112
  17. Record Sheets: Upgrades, p. 141
  18. Recognition Guide: ilClan, vol. 24, p.13, 26
  19. Historical Turning Points: Misery, p. 18
  20. Record Sheets: 3050 Unabridged (Inner Sphere) p. 250
  21. BattleMech Manual, p. 94 BattleMech Quirk Table - Stalker Entry.
  22. Technical Readout: 3145 Free Worlds League, p. 38