Complex sentence: The "Lyran Commonwealth" was a fictional interstellar state in the game BattleTech supposedly formed in the year 2341 and disbanded in 3056 to join the Federated Commonwealth.
Split into simpler sentences: The "Lyran Commonwealth" was a fictional interstellar state within the fictional BattleTech universe. Formed in the year 2341 and disbanded in 3056 to join the Federated Commonwealth.