From Halopedia, the Halo wiki
During the Insurrection, insurgent forces on Fumirole, as well as those on Hellas, utilized rumbledrugs in a vainglorious attempt to fight Spartans. Unencumbered by the body's normal safety limits, rumbledrug users were capable of feats of enormous strength, but the subsequent lack of control and mental instability, combined with immediate physiological damage, meant that users often died long before they ever laid hands on a Spartan. However, they dealt tremendous damage to themselves and anything that stood in their way.
Fumirole became the site of a battle in April 2552. On April 22, Kat-B320 of SPARTAN Noble Team attempted to carry a Fury tactical nuclear weapon aboard a Covenant CCS-class battlecruiser that was holding position over a city. She was wounded during her run toward the ship, destroying her arm. Thom-A293, another member of Noble Team, took the nuclear device and flew inside the ship; after he boarded the ship, he planted the bomb and attempted to escape. The device detonated while he was still aboard, destroying the battlecruiser but killing Thom.
A fumirole or fumarole is defined as an opening in a planet's crust that issues volcanic gases, perhaps indicating that Fumirole is a geologically unstable or volcanic world.
List of appearances