Which race(s) was said to spark the war of "Twilight Gap"?

I believe that was the Fallen?

Correct. The Battle of the Twilight Gap was one of the biggest battles ever faced by the City. This battle took place at the outskirts of the city, at the Twilight Gap. The Kell of the House of Kings manipulated the different Houses of the Fallen into joining forces to attack the City, with the House of Devils leading the charge. The House of Wolves would have joined the battle, had they not been caught off guard by the Reef. The ultimate goal for the Fallen was the capture of the Traveler. The City responded by organizing a force of Guardians under Vanguard Commander Saladin Forge.

Wow. I didnt know it was the Kings Kell that organised, or Saladin led the Guardians at Twilight Gap.

Do you know what weapon was made during this battle? Myth not 4 u ;)