Individuals tasked with hunting down and killing Omen. They wear masks with twisted horns carved to resemble the evil spirits seen by Omen in their nightmares[1], and wield paired cleavers affixed with severed Omen horns.[2] They wear aprons that evoke the garb of Rollo, the first Omenkiller[3], a famous perfumer who imbibed a physick to rid himself of emotion in order to carry out the extermination of the Omen.[4]
Moveset
Cleaver Slam
Phase
Slash
Can Be Parried
They jump forward, slamming both cleavers down. This attack can be chained up to three times. Roll towards them to avoid the attack, as rolling away will likely still get you hit by the cleavers. This is also a very telegraphed attack, so you have plenty of time to roll out of the way or parry.
Mask Flame
Phase
Fire
Cannot Be Parried
They lower their cleavers and jut their head forward. A spark will come out of their mouths, followed by a conical stream of fire. Run away from them to avoid being hit by the flames.
Mask Flame Retreat
Phase
Fire
Cannot Be Parried
They lower their cleavers and jut their head forward. A spark will come out as they leap backwards, leaving behind a patch of fire in the ground.
A magic user with a guided bolt-like spell such as Glintstone Pebble has a particularly efficient tactical option for this Omenkiller: the area he is in also contains two cabins. The double-jump of Torrent can easily get you onto the lower cabin, and from there another double-jump can get you onto the roof of the taller one. From there, the Omenkiller will not be able to reach you with any of his attacks. He does often get rather close to the wall of the cabin which can be difficult for you to hit, and at longer range (usually after a fire-breath when he backs up a bit) he tends to dodge attacks, but carefully timing your shots should slowly but surely allow you to kill this enemy solo at little risk.
These enemies are a fairly clear homage to the Capra Demons of the first Dark Souls, most clearly seen with having a very similar jumping slam attack (though a Capra Demon would only do one, while an Omenkiller will do three in a row) and the one that's most likely of each kind to be encountered first is found in the company of dogs that will harass the player when they attack.
Their model skeleton, used to model hitboxes, even has the same, small tail as Capra Demons do (though this has no effect on their hitboxes in either case).
Rather bluntly referred to in in-game files as "Slaughter" (compare with the Omens that they hunt, who are referred to as "ShunnedChild").
