Crumble Undead was a spell that required a Magic level of 39 and could hit a maximum of 150 life points to undead monsters, which included:
- Crawling Hands, Skeletal hands, Zombie hands
- Zogres, Skogres
- This spell was removed with the Evolution of Combat update.
- Strangely, despite being technically classified as undead, it did not work on the Barrows brothers, the Banshee Champion, certain high-levelled Revenants, mummies, Count Draynor (or other Vampyres), Dragith Nurn, or Nazastarool.
- It was an inexpensive method for players who wanted to spend minimal money to train magic, as it hit as high as Earth Blast but was cheaper than Earth Bolt.
- Attempting to cast Crumble Undead on anything other than undead monsters would yield the message "This spell only affects skeletons, zombies, ghosts and shades".
- In RuneScape Classic, Crumble Undead gave 98 experience per shot.
- Crumble Undead was not available in the Daemonheim spellbook.
- Prior to the 2 September 2009 update which allowed any staff to autocast any spell, Crumble Undead was only able to be autocast by using a Slayer staff or a Void Knight mace.
- The spell animation suggested that it was an Area of effect attack, however this was not the case.
- The Mindspike's special attack did not work when casting Crumble Undead.