The Devolin system was a star system in neutral territory close to both the United Federation of Planets and the Romulan Star Empire. The system contained a great deal of ionizing radiation and contained a large asteroid field.
In 2358, the USS Pegasus drifted into the system, having suffered heavy damage from a large explosion in main engineering. The ship was testing an experimental (and illegal) phasing cloaking device. Still in a phased state, the ship passed in to a large asteroid, at which point the cloak failed and the ship dephased, with around two-thirds of the ship materializing inside solid rock. The explosion, along with the hull breaches caused by the failure of the cloak, killed everyone aboard.
In 2370 the Romulan warbird IRW Terix entered the system and discovered wreckage from the Pegasus. Starfleet learned of this and dispatched the USS Enterprise-D to locate the ship first. They were successful, but their attempts to recover the phasing cloak were hindered when the Romulans sealed the Enterprise inside the asteroid. The Enterprise was able to escape using the phasing cloak to pass through the rock. (TNG: "The Pegasus"; ENT: "These Are the Voyages...")