Superior slayer monster - OSRS Wiki
Superior slayer monsters are more powerful versions of normal slayer monsters that have a 1/200[1] chance to spawn upon the death of one of its normal counterparts. They can be encountered after purchasing the unlock Bigger and Badder for 150 Slayer reward points from any Slayer master, and will only occur while on a Slayer task. This can be toggled on and off afterwards without loss of points.