- Slayer is a Mastery that offers rewards for various numbers of monsters killed.
- Skeleton Soldiers were formerly (prior to Slayer Edition) known as "Bandit Skeletons".
- Skeleton Warriors were enemies that have been essentially transformed into what are now known as Skeleton Defenders. Skeleton Warriors had a slightly different attack set and appearance but were largely similar to what Skeleton Defenders are now in many ways, including their use of a sword and shield, as well as spawning in the same locations in the game.
- Skeletal Archers were enemies that have now been removed. Their removal was presumably for the purpose of making them the summons of Necromancer's weapon, Necrotic Vessel, as they are extremely similar.