System L-374 was an uninhabited planetary system with four planets in the Beta Quadrant. This system, and the L-370 system, were located in the same sector. The Rigel system was close to this system.
The system was attacked by the "planet killer" in 2267. It had four terrestrial worlds that were charted prior to the attack; the surface temperature of one inner planet was that of molten lead and another had an atmosphere poisonous to Humans; the two outer planets were consumed as fuel by the machine before it could be destroyed by the starships USS Enterprise and USS Constellation. (TOS: "The Doomsday Machine")
The quadrant of origin for this planet was inferred from the trajectory of the planet killer. This ancient machine destroyed, in this order, L-370 and L-374 and the next system targeted was the Rigel system. This system had been established to be in the Beta Quadrant by star charts seen in Star Trek: Enterprise, Star Trek: Discovery, Star Trek: Picard, Star Trek: Strange New Worlds, and Star Trek: Section 31.