Mature grotworm

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Mature grotworms are monsters that can be found on the bottom level of the Grotworm Lair. They have slow, but extremely accurate, magic attacks, their melee attacks however have very low accuracy (It should be noted that, due to the recent changes on the combat system, this grotworms are no longer especially accurate or dangerous for players with a combat level of 160 or higher). However, magic attacks are only used on players outside of melee range, similar to monsters such as metal dragons and cockroach soldiers. It is possible to safespot them using the pillars if you stand far enough back from them. Lower-level players are recommended to bring high healing food such as monkfish or sharks. Ranged/magic would require Protect from Magic/Deflect Magic if using safe spots. The magic attack has a short range, so flashing your prayer when out of its range can help conserve prayer points.

Using high level ranged gear such as Armadyl and using a bunyip will mean you won't need prayer pots/flasks. Due to the occasional shark drops, at most you should only need 1 or 2 pieces of food as your gear will mean little damage from the mature grotworms magic attack while ranging.

If a player tries to setup a cannon within the Grotworm Lair a message will be visible in the console saying: "The damp air would prevent your cannon operating."

Some players may find it useful to bring runes to cast High Level Alchemy on the items dropped by the grotworms, as adamant and rune equipment are common drops. The profit of using High alchemy on some of these items is greater than banking and selling them.

Botting mature grotworms in this lair is rampant. Upwards of 30 bots can be found on the east side of the cave, often making it a more viable option to complete a Grotworm Slayer task by killing regular grotworms.

100% drop

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Weapons
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Armour

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Herbs

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Seeds

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Raw Materials

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Other

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Trivia

 * When these creatures were first released, they did not drop items from the rare drop table, but did after the Queen Black Dragon update.
 * The word 'grotworm' means caveworm in Dutch.
 * Their examine text hints towards the possibility of the existence of a stronger grotworm based creature, although likely not an actual worm as "metamorphosis" implies, but none were released with them.
 * Due to excessive botting, an update on 7 August 2012 removed several rune armour drops from the drop table of mature grotworms, replacing them with their adamant counterparts, making it less effective to earn money. The same update also removed royal bolts from their drop tables.