Horror from the Deep

Walkthrough
Although this quest is short, it is made troublesome by two hard monsters to be defeated, the Dagannoths.

Getting started
A Camelot teleport is useful(1 law rune and 5 air runes),or bring a ring of duelling.

Start by speaking to Larrissa north of the lighthouse. Items to take with you now are: nails, hammer, swamp tar, tinderbox, molten glass,1 fire rune, 1 water rune, 1 earth rune, 1 air rune, 1 arrow, and 1 sword. (last six items cannot be retrieved.)

Fixing the Lighthouse

 * 1) After speaking to Larrissa, go south, jump across the basalt platforms and go to the Barbarian Outpost.
 * 2) Talk to Gunnjorn and get the lighthouse key; you can get your two planks here, which respawn north of Barbarian's Outpost.
 * 3) Use both planks on the broken bridge east of Larrissa (needs some walking).
 * 4) Go and talk to Larrissa again.
 * 5) Go up to the second story.  Search the bookcase and take all the books available, flip through the lighthouse manual and the Ancient diary. (The journal plays no part in the quest).
 * 6) Go up one more level, use the following items on lighting mechanism in this order: swamp tar, tinderbox, molten glass. The lighthouse will now be fixed.

The Door
Go to the bottom floor of the lighthouse then 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 can save some time.  If you hadn't, teleport to Camelot or walk to bank.
 * 3) Get good armour (Rune or better), or mage armour (Mystic or better) 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. Equip a ring of life or bring a one-click teleport just in case things get twisted.

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 colour if you want to do any damage more than 1 or 2.
 * White means you should use wind spells.


 * Blue means you should use water spells.


 * Brown means you should use earth spells.


 * Red means you should use fire spells.


 * Orange means you should use melee.


 * Green means you should use ranged.

!NOTE! you can kill the baby dagannoth, then run away after you have talked to Jossik again, and still battle the mother next time you go there(even if you log out)

Note
If you cannot see the colour changes very well, look at the chat box. Using the wrong attack does no damage to it. Also there is a safe spot, if you do it right you can get the mother stuck behind a rock were you can stand behind and not lose any hit points.

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, so Protect from Melee is recommended. Also if you "don't" have ranging items, you can keep clicking under her so she doesn't hit you, or simply hide behind a stalagmite.

Do not bring a summoning familiar, as it will rarely ever hit because when fighting, the familiar won’t alternate attacks and it will simply waste time and resources to switch between familiars every thirty seconds.

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

You can now choose one of the three damaged prayer book you want (Zamorak, Guthix, Saradomin) from Jossik.

Reward

 * 2 quest points
 * 4662.5 magic experience
 * 4662.5 strength experience
 * 4662.5 ranged experience
 * A damaged prayer book of your choice: a Holy book (Saradomin), an Unholy book (Zamorak), or a Book of balance (Guthix).
 * Access to the lighthouse general store and the Dagannoth caves underneath (There are level 74 and 92 Dagannoths. The level 74's use a ranged attack that has terrible aim, and the level 92's use their much more effective melee attack)