Giant rock crab

Giant Rock Crabs commonly referred to as GRC are massive versions of the weaker Rock crab. They lie in wait for prey, disguised as large boulders. When approached, they attack, unless they have become tolerant, in which case they remain as "boulders" - attempting to cast a spell on them gives the message "You can't attack this npc"

Locations

 * In Waterbirth Island Dungeon (requires a partner to access)
 * In the Chaos Tunnels (The middle south rift just east of Mage of Zamorak (Abyss) leads directly to them). Recommended when not having a companion. They are easy to kill from level 67 or higher depending on skills wear rune or higher dragon weapons are recommended. A regular drop average.

Strategy


Giant Rock Crabs are very strong and extremely resistant to Melee and Ranged attacks, and thus are only effectively killed using Magic. However, Verac's armour is quite effective with its unique set effect, which can hit through the tough rock-hard armour, and also has a prayer bonus allowing the player to use Protect from melee for longer than usual. This method is advised for those with a low Magic level but high melee combat levels. They can drop three charms at once. The crabs are not immune to poison, but it is extremely difficult to hit them with a poisoned weapon like the dragon dagger.

Diamond bolts (e) can also ignore the ranged defence of Giant Rock Crabs, although using them might not be very economical.

A notably effective and economic way to kill Giant Rock Crabs is the Black Salamander. The Black Salamander's magic attack acts as a normal magic attack, thus being effective against the rock-hard armour, and since the Giant Rock Crabs' magic defence is so low, so you can utilise high level defensive armour without losing much accuracy.

Giant rock crabs do have a very high defence, but a relatively low attack/strength. If attacked in the Chaos Tunnels they will walk off and stop attacking you after a minute or two.

An easy way to mage/range them is to use the Chaos Tunnels entrance north of Varrock. To do this, get your best mage/range armour that you have, and go to the Grand Exchange. North-west of the counters is a small under-wall tunnel. Go through it, and head north along the river until you see a Mage of Zamorak that you can trade with. Head north-east from there till you see a rift with a rope in it. Go through it, and you should see a small area with a lot of boulders. Head to the north-east most part of it, where there should be a portal. North of that is a crab boulder and a few stalagmites. Wake up the crab there and go north of the stalagmites. You should be able, from here, to mage/range to the crab without taking any damage. A great method is using Fire Bolt and Chaos Gauntlets. Wearing Mystic and a decent shield for when they get too close to you (Lunar equipment or Splitbark armour are also acceptable), bringing Excalibur from Merlin's Crystal Quest (or Enhanced excalibur from the hard tasks in Seers' Village Diary) will help otherwise. Using this method you can average a bit above 100 charms and 35k exp per hour while spending under 100k. You can also afk with sound on, it takes about 2 min before it starts to retreat, then you can turn on your prayer if too many aggro.

If using mage, note that they are most vulnerable to air-based spells.

Mage Gear is as follows:
 * Helmet: Farseer helmet
 * Necklace: Amulet of glory, Amulet of magic, Amulet of power, Amulet of fury, or an Amulet of accuracy
 * Cape: God cape, Obsidian cape, or Cape of Accomplishment
 * Plate: Mystic robe top
 * Legs: Mystic robe bottom
 * Weapon Slot: Elemental staff of Air; optionally use an elemental staff of Fire, Lava, or Steam if using Fire Bolt
 * Shield: Completed Unholy book, Mage's book, Arcane spirit shield, Dragonfire shield, or Dragon Square Shield
 * Gloves: Barrows gloves or Chaos gauntlets
 * Boots: Wizard boots, Infinity boots, or Mystic boots
 * Ring: Beacon ring, Explorer's ring, Lunar ring, Ring of wealth, or Seers' ring

Retreat
The Giant Rock Crab is one of few monsters in RuneScape that will retreat from battle when they become critically wounded. One way to avoid this (in the southern room in the chaos tunnels) is to kill the eastern one first (using the safespot in the picture above). Then when picking up the drop from him you will have probably alerted a few other giant rock crabs. Go back to the safespot and two should follow you there, from there kill them. While you're killing them the one you first killed should spawn but not attack (unless you go beside it). Because he spawns the other two can't get out and are trapped, so they cannot retreat. After killing the first one, don't pick up the drop and proceed to kill the 2nd one. This means that you will not alert the one that spawned and you will have another retreat free kill. Do this over and over.

27 May 2009
After the 27 May 2009 update, Giant Rock Crabs drop Charms in groups of three instead of ten. However, charm dropping rate was increased significantly. This hidden update angered players, though complaints died down as the rate of dropping them was increased.

100% drop

 * Bones - the giant rock crabs drop bones, even though crabs are invertebrates, both in real life and apparently in RuneScape (since all other crabs do not drop bones)

Runes

 * 1-39 Water runes
 * 2-37 Earth runes
 * Nature talisman
 * Air talisman
 * Mind talisman
 * Fire talisman
 * Cosmic talisman
 * Body talisman
 * Water talisman
 * Chaos talisman

Weapons and armour

 * Steel platebody
 * Black claws
 * Black warhammer
 * Black platebody
 * Mithril hatchet
 * Adamant longsword
 * Adamant warhammer
 * Rockshell gloves
 * Rockshell boots
 * Rock-shell splinter
 * Rock-shell chunk
 * Rock-shell shard

Charms
Please add your charm drop rates to the next template: 

Seeds

 * Poison ivy seed
 * Herb seed
 * Belladonna seed
 * Snapdragon seed
 * Torstol seed

Herbs

 * Grimy irit
 * Grimy cadantine
 * Grimy ranarr
 * Grimy marrentill
 * Grimy kwuarm
 * Grimy dwarf weed
 * Grimy tarromin
 * Grimy guam
 * Grimy avantoe
 * Grimy harralander

Other

 * 27, 70, or 137 coins
 * Uncut gems
 * Raw lobster (common)
 * Raw bass (common)
 * Casket (very rare)
 * Tinderbox
 * Level 2 clue scroll