Lava monsters, also known as Tz-Kils, are creatures found along the path to the Elder Kiln. They use a powerful magic attack which can hit almost 300. Protect from Magic or Deflect Magic is advised against these monsters to reduce damage taken their attacks.
Despite their fairly high combat level and dangerous maximum hit, they have few life points and low defence, and are usually taken down in a few hits with a good crossbow. It is a good idea to leave a lava monster blocking the TokTz-Ket-Dill for last, as the latter deals melee damage which must not be prayed against or it would deal high amounts of unblockable damage.