In the past, this particular dragon held a grudge against Toothless due to some past confrontation that resulted in Toothless leaving a distinctive scar on the Whispering Death's hide where he bit the other dragon, forming a rivalry between the two. The Whispering Death eventually made its way to Berk where it encountered Toothless once again and immediately saw that the Night Fury was grounded due to his tail being damaged. It gained advantage over Toothless due to his inability to fly, striking the Night Fury in the leg with one of its spines. Before it could continue its assault, the Whispering Death was forced to retreat underground when sunlight falls on it.
Hiccup attempted to train the Whispering Death to stop its attack on Toothless, but none of his tactics had any effect on the wild dragon, and Toothless and his rival engaged in another battle. Although Toothless tried to fight it on his own, his inability to fly put him at a disadvantage. The Whispering Death nearly killed Toothless by cornering him into a canyon, but it was only after Toothless accepted Hiccup's help that the wild dragon was overpowered. As Toothless was about to kill the Whispering Death to end their rivalry once and for all, Hiccup stopped Toothless, and the Night Fury allowed the Whispering Death to flee. After it was driven away, the holes it made through its burrowing were blocked up with boulders.