On the USS Farragut's visit in 2257, a Dikironium cloud creature killed over 200 Farragut personnel, including the Farragut's commanding officer, Steve Garrovick. Then-Lieutenant James Kirk survived the ordeal.
In 2268, now-USS Enterprise Captain Kirk returned to Tycho IV to determine if it was the Dikironium cloud creature's home. Kirk and Garrovick's son, Steven, beamed down with an antimatter bomb. The bomb destroyed the creature and ripped half of Tycho IV's atmosphere away. (TOS: "Obsession")