This sound is from Grey Knight Warhammer 40k Soundboard

The Grey Knights are a secret, mysterious Loyalist Chapter of Space Marines specifically tasked with combating the dangerous daemonic entities of the Warp and all those who wield the corrupt power of the Chaos Gods. They have the honour of being implanted with gene-seed engineered directly from the genome of the Emperor Himself. The Grey Knights act as the military arm or Chamber Militant of the Ordo Malleus, the Daemonhunters who form the oldest branch of the virtually omnipotent Inquisition.