Cow31337Killer is a spoof of an adventurer occurring during the Animal Magnetism quest. He kills an undead cow, and attempts to kill an undead chicken during a cutscene. He is shooed away and can't kill the chicken.
He has a combat level of 123 (though he is unattackable), and wears a rune platebody, rune plateskirt, rune boots, Klank's gauntlets from the Underground Pass quest, a custom brown cape with a yellow trim on the bottom, with a Dharok's helm and a Dharok's greataxe. His name appears to be "Cow Elite Killer" in Leetspeak.
- Previously, this NPC was known as Cow1337killr.
- During the 2017 Birthday event, Cow31337Killer attends Party Pete's Birthday Bash. Towards the end of the event, he kills a mugger who set out to kill the partygoers.
- While being a parody of a player, his name is too long for an actual player to take as its length exceeds 12 characters.
- He appeared in the 2018 Birthday event.