Slagilith

The Slagilith is encountered during the One Small Favour quest in the Goblin Cave, when the player uses the Animate rock scroll intended to free Petra from the rock face, but accidentally animates some rocks nearby. It hits somewhat hard, and has very high defence, but it does not hit very often.

Protect from Melee is recommended as it can hit up to 260 LP, although it is wildly inaccurate. Like earth elementals, pickaxes work well against it. High-level players should have no problem dispatching this monster, assuming they bring a good weapon and armour. It drops adamantite ore, an uncut diamond, and an uncut ruby when defeated.

Slagilith cannot be challenged again once it has been defeated once during One Small Favour, so this monster cannot be used to repeatedly obtain its drops which sell for a good amount of money when combined.

It is recommended that you kill it with a pickaxe, perhaps rune or dragon, otherwise you will only do minimum damage.

Trivia

 * The word Slagilith was censored in chat, because "slag" is a term for a prostitute. This has been fixed.
 * This monster bears a huge resemblance to the monsters in the Living Rock Caverns, although not as well animated (since Slagilith was released before RuneScape HD).