Official notes
Official wiki for this creature. Official news wins.

You already know the room. The creature is the constant. You are the variable.
They teleport a few tiles. Do not plant.
Slayer · Old School RuneScape
Where
Slayer Tower, Catacombs
Slayer
Chaeldar, Konar, Nieve/Steve, Duradel.
Hunt
Slayer Tower floor or Catacombs multi. They melee and teleport a few tiles — do not plant on the tile they just left. Protect Melee. Tower is single; Catacombs is the burst room. Cannon stays out of the Tower. Slayer helm on task. They melee and teleport a few tiles. Do not plant on the tile they just left. Protect Melee. Catacombs is the burst room. Cannon stays out of the Tower.
Watch
They teleport a few tiles.
Kill
A kill ends when abyssal demon drops. Walk the room if you pulled extras. Reset at the door when the task is done. Wrong prayer or the wrong tile is the wipe. That is the whole file. Do not treat a slayer floor as a raid invocation. Counts, drops, and the living method: the Old School wiki for this hour.
Live wiki · Slayer task · Same name in the other game · Use on banner