The Slayer master is located in the Slayer hub which can be teleported to by using the hotkeys CTRL+S. She gives out three tasks to adventurers: short, medium and long. These tasks change the amount of kills a player is assigned. The monster difficulty automatically increases with the Slayer level. For instance, at level 1 Slayer players might be assigned 10 Chickens as a short task, but at level 99 Slayer, they could be assigned 10 Abyssal demons.
For more information about Slayer, see Slayer.