During the Imperial Era, stormtroopers clad in black armor, known as volcanic environment stormtroopers or lava troopers, were stationed at Fortress Vader. This castle, the residence of the Sith Lord Darth Vader, was located on the planet Mustafar. These specialized troopers, equipped with E-11 blaster rifles and protected by heavily cooled, heat shielded armor, defended the fortress against various threats. Around 12 BBY, they fought off attacks from the native Mustafarians. Approximately eleven years later, they encountered the Rebel Alliance crew of the YT-1760 Small Transport Auric after the group became stranded on Mustafar. Furthermore, between 3 and 4 ABY, the volcanic environment stormtroopers defended the fortress from the Force-sensitive warriors known as the Knights of Ren during their heist on Vader's Castle.
During the age of the Galactic Empire, the Human soldiers known as volcanic environment stormtroopers, alternatively called lava troopers, acted as the defense force for Fortress Vader. This fortress was the stronghold of the Dark Lord of the Sith Darth Vader situated on the planet Mustafar. These volcanic environment stormtroopers had a similar role to magmatroopers, who were also tasked with the defense of Vader's castle.
The volcanic environment stormtroopers were distinguished by their black stormtrooper armor, which was equipped with advanced cooling mechanisms and heat shields. They also had back-mounted tanks and distinctive red breathing tubes. A red line on the right shoulder pauldron identified sergeants, while other troopers wore a fully red pauldron. They were armed with E-11 medium blaster rifles.
Shortly after Fortress Vader was constructed, around 12 BBY, two volcanic environment stormtroopers were on duty in the castle's hangar bay. One trooper, hearing a "clunk," asked his colleague if he had heard the same. He demanded that whoever made the noise identify themselves. However, Mustafarians invaded and quickly overwhelmed the pair.
Around the same year, two volcanic environment stormtroopers were guarding a landing platform outside Darth Vader's castle when they noticed an incoming Theta-class shuttle, an unusual sight for that time. After a brief discussion about shuttles, they were startled by a wailing sound and went to investigate. The sergeant attributed the sound to the wind, but the other questioned this as they were surrounded by zombies, victims of a plague. The sergeant was bitten and attacked the junior trooper, who reported the incident to Darth Vader before succumbing to the infection. Both victims, now controlled by the Mustafarian priestess Mother Sssl, joined the undead horde in attacking Vader. The junior trooper managed to bite the cyborg Sith Lord, though it only damaged his metal and had no other effect.
Around 1 BBY, two volcanic environment stormtroopers were on guard outside Fortress Vader when the YT-1760 Small Transport Auric, a starship owned by Commander Lina Graf of the Rebel Alliance, crash-landed on Mustafar. Subsequently, seven volcanic environment stormtroopers ambushed Graf and her crew, opening fire with their blasters. Graf returned fire and ordered her crew to retreat to the fortress. The lava troopers then attacked the bodyguard droid XM-G3, who stayed behind to defend Graf, keeping the troopers occupied. XM-G3 later emerged visibly damaged but victorious. At least four volcanic environment stormtroopers were guarding the castle's hangar bay when Graf's technician Skritt distracted them during the crew's escape. He tossed a Kubaza beetle larva, summoning its much larger mother. The rebel bowled over a pair of the soldiers and commandeered an All Terrain Scout Transport, opening fire on the remaining troopers.
Sometime between 3 ABY and 4 ABY, when the Knights of Ren, a group of Force-sensitives, broke into Fortress Vader, Vader's attendant Vaneé activated an alarm, summoning a contingent of volcanic environment stormtroopers. The Knights prioritized engaging the soldiers, which allowed their leader, "Ren," to access Vader's vault and steal a Force artifact known as the Screaming Key. After the theft, Ren inquired if his Knights had ceased firing their weapons because all the troopers were dead. Vader then revealed himself and stated that he had dismissed the lava troopers.
Volcanic environment stormtroopers made their debut in the first issue of the Star Wars Adventures: Tales from Vader's Castle comic series, authored by Cavan Scott with illustrations by Derek Charm and Chris Fenoglio. IDW Publishing released the issue on October 3, 2018. They were later identified as lava troopers in the series' fifth issue, which IDW published again on October 31, 2018. Scott also wrote this issue, while Charm and Charles Paul Wilson III provided the pencils. The formal designation "volcanic environment stormtroopers" was given in Star Wars: Dawn of Rebellion: The Visual Guide, a 2023 reference book written by Pablo Hidalgo and Emily Shkoukani. Within the Star Wars Legends continuity, the term "lavatrooper" was originally an alternative name for the red-armored magma stormtroopers.