Deathleaper

Deathleaper was the name given by the Imperium of Man to a unique Tyranid of the Lictor genus which did much to hasten the downfall of Imperial world St. Caspelan in Games Workshop's Warhammer 40,000 universe.

History
Once a world with a powerful, well disciplined and highly motivated military, St. Caspelan was ruled by the charismatic Cardinal Salem. Somehow becoming aware that the planet would be no pushover, the oncoming Hive Fleet Leviathan deployed one of its most terrifying psychological weapons, Deathleaper.

Knowing on an instinctual level that simply murdering Salem would do nothing more than create a martyr for the humans to rally around, Deathleaper opted for a different approach. Every night for ten nights it effortlessly infiltrated the Cardinal's command bunker, slaughtering all of his aides and bodyguards but disappearing back into the shadows at the last minute, leaving behind only Cardinal Salem, covered in the blood of his staff.

Knowing that he lived only by the grace of an inhuman assassin proved too much for the Cardinal, and his sanity broke, causing him to degenerate into a creature of paranoia. This shattered the morale of the men under his command, along with their faith in themselves, and left St. Caspelan wide open to a full-fledged assault from the Hive Fleet which they did not survive.

What became of Deathleaper in the aftermath is unknown, but there have been no further reports of its activities. This may be due to the fact that Tyranids re-absorb all genetic material back into their Hive Ships after a planet is successfully conquered. However, the possibility remains that Deathleaper has performed his function on other worlds, and there has simply been no record left to tell.