Finally got these, after having the required level for ages.
Quite weak for their level, I was trying out my new bandos godsword, hitting 40+ on them. They are next to Gargoyles in the Canifis Slayer Tower.
They drop rune boots, as well as a few rune items. They summon death spawns to help them, but these aren't worth dealing with. Bunyip is useful here, to heal the small damage taken.