Horror from the Deep

Walkthrough
Although this quest is really short, it is complicated by two very hard monsters to defeat, the Dagannoths.

Getting Started
Teleporting to Camelot is helpful; if you can bring 1 law rune and 5 air runes

Start by speaking to Larrisa north of the lighthouse. Items to take with you now: nails, hammer, swamp tar, tinder box, molten glass, 1 of each elemental rune, 1 arrow, and 1 sword.

Fixing the Lighthouse

 * 1) After speaking to Larrisa go down south of her jumping across the basalt platforms and into the Barbarian Outpost.
 * 2) Talk to Gunnjorn and get the key to the lighthouse; you can get your two planks here, which respawn north of Barbarian's Outpost.
 * 3) Use both planks on the broken bridge east of Larissa.
 * 4) Go and talk to Larrisa again.
 * 5) Go up to the second story.  Search the bookcase and take all the books, flip through the lighthouse manual and the Ancient diary.
 * 6) Go up one more level, use the following items on lighting mechanism in this order: swamp tar, tinderbox and then, Molten glass.

The Door
Use all of your basic elemental runes on the door, (fire, water, earth, and air)
 * 1) Use your sword (any type, but you will not get it back), and your arrow (any type, but you will not get it back).
 * 2) If you brought your stuff for the fight, then you saved time.  If you hadn't, teleport to Camelot or walk.
 * 3) Get good armor (Runite), or mage armor (Mystic) bring many mind, chaos, death, or blood runes and enough runes to cast several of each elemental spell. (wind, water, earth, and fire), get a good weapon for melee, and some ranger equipment.

The Fight

 * 1) Go though the door and down the ladder.
 * 2) Talk to Jossik, be prepared to fight two Dagannoths.
 * 3) The first one is easy, put on protect from melee and range or melee it, because you want to save your runes for the mother.
 * 4) Then right after you defeat it, there will be a cut scene, and you will fight a harder monster.
 * 5) You should attack the Dagannoth Mother by color if you want to do any damage more than 1 or 2.
 * White means you should use air spells.


 * Blue means you should use water spells.


 * Orange means you should use melee.


 * Brown means you should use earth spells.


 * Red means you should use fire spells.


 * Green means you should use range attacks.

Note
If you cannot see the color changes very well, look at the chat box. Using the wrong attack does no damage to it.

The best way to defeat her is to ignore the ranged and melee forms, since she has too high defence against those attack types for them to be worthwhile. Use an air staff and switch spell types in the correct order.

She can detect prayer, and will automatically use the opposite attack type when you use prayer. By default, she ranges at a distance and melees up close. Her melee attacks are stronger.

After the fight
You'll get a rusted casket after you defeat the Dagannoth Mother. Go to the second floor of the lighthouse and show it to Jossik to finish the quest.

Reward

 * 2 quest points
 * 4662.5 magic experience
 * 4662.5 strength experience
 * 4662.5 ranged experience
 * A damaged prayer book of your choice (Saradomin, Zamorak, or Guthix)
 * Access to the lighthouse general store and the Dagannoth caves underneath (There are level 74 and 92 Dagannoths. Both use a ranged attack that has terrible aim, but the level 92 ones will try to use their much more effective melee attack whenever they can)