Horror from the Deep

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

Getting Started
A Camelot teleport is useful if you have the Magic level and 1 law rune and 5 air runes, or a Games necklace also works.

Start by speaking to Larrisa outside of the lighthouse. You will need: 60 steel nails, a hammer, swamp tar, a tinderbox, 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 (in the Barbarian Outpost Agility arena) and get the lighthouse key; you can get your two planks here, which respawn north east of Barbarian's Outpost.
 * 3) Use both planks on the broken bridge east of Larrissa.
 * 4) Go and talk to Larrissa again.
 * 5) Go up to the first floor. Search the bookcase and take all the books, flip through the lighthouse manual and the Ancient diary.
 * 6) Go up one more floor, use the following items on lighting mechanism in this order: swamp tar, tinderbox, molten glass.

The Door
Go down the iron ladder into the basement to find the door.
 * 1) Use all of your basic elemental runes on the door (fire, water, earth, and air).
 * 2) Use your sword (any type, but you will not get it back), and your arrow (any type, but you will not get it back).
 * 3) If you brought your stuff for the fight, then you saved time. If you hadn't, use your Games Necklace to go back to Barbarian Assault and bank there.
 * 4) Get good armour (Runite), or mage armour (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 through the eastern part of the door and down the ladder.
 * 2) Talk to Jossik, be prepared to fight two Dagannoths.
 * 3) The first one is easy if you have Protect from Melee. If you don't have Protect from Melee and your combat level is relatively low, it might be wise to safespot behind the rocks in the room. It can be killed by all forms of combat.
 * 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 deal any damage.
 * White means use air spells.


 * Blue means use water spells.


 * Orange means use melee.


 * Brown means use earth spells.


 * Red means use fire spells.


 * Green means 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. Also, you can safespot her by using the stalagmites in the room. If you do it right, you can get the mother stuck behind a stalagmite were you can stand behind and not lose any health 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.

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.

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. 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.)

Trivia

 * Unlike most quests, the reward screen for Horror from the Deep says 'You have survived the Horror from the Deep!' rather than 'You have completed the Horror from the deep!'