Mr. Murderous Pile of Yak Dung is a minor antagonist from Dragons: Race to the Edge, who appeared in the episode, Guardians of Vanaheim. Although his voice actor was not mentioned in the credits, he was likely voiced by James Arnold Taylor.
At some point before the episode main events began, Mr. Murderous Pile of Yak Dung and other Flyers were sent by Johann and Krogan on a mission, and eventually discovered the island of Vanaheim by following Heather to it. He and the other Flyers attacked the Sentinel dragons guarding it, and decided to inspect it, since they thought the skull on the island belonged to the "King of Dragons." He was apparently left behind by the others at some point.
He was later confronted and captured by the Dragon Riders. Ruffnut and Tuffnut were asked to watch over him. Tuffnut nicknamed him Mr. Murderous Pile of Yak Dung. Since he is one of the Dragon Flyers, the twins asked him about what it is like, when there is a vacation or if he has healers. He replied that the healer's name is Jorn. They also aked him about career change.
Later, the twins brought him to the hut, then he stole the Dragon Eye Lens and jumped to the bushed and he got injured, then the Grim Gnasher Dragons attacked him. It is unknown if the dragons killed him or if he survived the attack.
Mr. Murderous Pile of Yak Dung appeared to be similar to other Dragon Flyers, the ones that ride on Singetails. He also has a helmet like his companions. His shirt appears to be made of dragon skin. He also has some face painting similar to Dagur the Deranged.
Once he met the twins, he appeared to be friendlier to them. They talk to each other about what being a Dragon Flyer is like. Despite his affable personality, he was still loyal to his masters and had no problem with killing or attacking anything in his way.