|Manufacturer||Defiance Industries of Hesperus II|
|Chassis||Foundation Type 220 Endo Steel|
|Armor||Durallex Special Heavy V2 with CASE|
|Communications System||Angst Discom /w Guardian ECM|
The Fafnir was intended to become Defiance Industries of Hesperus' flagship BattleMech. The slow assault design serves as a platform for the pair of "Thor's Hammers". The Fafnir is built on a lightweight Foundation Type 220 Endo Steel chassis that is capable of supporting the Fafnir's massive weapons payload and armor while weighing half as much as a standard chassis. To power this massive 'Mech, a Vlar 300 fusion engine gives the Fafnir a top speed of 54 km/h. The Fafnir is protected by nineteen and a half tons of Durallex Special Heavy V2 armor, giving it almost as much armor as the entire mass of some light 'Mechs. The Fafnir has CASE in both of its side torsos to protect it from secondary damage if one of the Heavy Gauss Rifles are damaged. Finally, for protection from enemy electronic warfare systems, the Fafnir has a Guardian ECM Suite.
Based on the heaviest chassis available, the Fafnir sports two of what was the Lyran Alliance's newest weapon in the early 3060s, the Heavy Gauss Rifle. The largest non-artillery weapon in existence, the Hammerfists can deal an immense amount of damage very quickly. Four tons of ammunition for each keep the weapons in good supply. The Fafnir cannot operate far from supply lines, however, as it only has two ER Medium Lasers and a Medium Pulse Laser as backup.
- A lack of Thor's Hammers during the FedCom Civil War forced engineers to come up with a field modification that could be useful without the Heavy Gauss Rifles. The solution was to replace them with paired standard Gauss Rifles, ER Medium Lasers, and an ER Large Laser. A lack of enough ammo plagues the 5B, but the use of energy weapons does make the design more viable without the ammunition. It does not come with enough additional heat sinks, however, so MechWarriors must be mindful of their heat levels. BV (1.0) = 2,230, BV (2.0) = 2,625
- This variant removes all the standard weaponry. It carries an Ultra Autocannon/20 in each arm, while the side torsos each mount a pair of Light PPCs. A Light Fusion Engine is used to provide power, and Light Ferro-Fibrous armor provides protection. Twelve Double Heat Sinks are hardly enough to keep this variant's heat under control. BV(2.0)=2,234
- This variant makes use of a pair of massive experimental Improved Heavy Gauss Rifles, and removes the pulse lasers to provide six tons of ammunition for the two guns. The ER Medium Lasers are left untouched. These models were used by the Skye Guards during the Coalition attack of Terra. BV (2.0) = 2,610
 Custom Variants
- FNR-4A Fafnir Peter
- This was a salvaged command 'Mech piloted by Archon Peter Steiner-Davion during the occupation of Tharkad from 3067 to early 3072. This customization removes the left torso Heavy Gauss Rifle, half the ammo for the HGRs, the left torso CASE, and the ER Medium Lasers. It has been fitted with ten Rocket Launcher 10s. Also in the left torso are two Extended Range Large Lasers. In each of the arms and in the head, a Medium Pulse Laser been added. It makes use of a Compact Gyro, making room for one of the ten launchers, a Guardian ECM Suite, and a C3 Slave Computer. BV (2.0) = 2,458
 Notable Pilots
During the campaign for Tharkad at the end of the FedCom Civil War, Peter Steiner-Davion led his pan-Lyran coalition from the seat of a brand new Fafnir. During the climactic street-to-street fighting in Tharkad City, he used it to defeat his great-aunt Nondi Steiner in a one-on-one fight. He later used a salvaged Fafnir during the siege of Tharkad that took place during the early part of the Jihad.
A Fafnir from MechWarrior 4: Mercenaries in motion
- ↑ MUL online date for the Fafnir
- ↑ Technical Readout: 3067, p. 101
- ↑ Record Sheets: 3067 Unabridged, p. 175
- ↑ Combat Operations, p. 131
- ↑ Record Sheets: 3067 Unabridged, p. 176
- ↑ Record Sheets: 3067 Unabridged, p. 177
- ↑ Record Sheets: 3067 Unabridged, p. 178
- ↑ Technical Readout: 3085, p. 191
- ↑ Record Sheets: 3085 Unabridged — Old is the New New, p. 121
- ↑ Jihad Turning Points: Tharkad, p. 2, 13. The record sheet includes a hand actuator where it should have the fourteenth endo-steel slot.
- ↑ Jihad Turning Points: Tharkad, p. 2