Introduction : Scarlet Monastery is many people's favorite instance. You will get to love it yourself too. One of the reasons people love it is because it is divided in 4 Mini instances instead a single big one. The advantages of that feature are numerous. The 4 mini-instances of Scarlet Monastery are The Graveyard, The Library, The Armory and The Chapel..
I will cover the graveyard instance shortly here (because there isn't much to say about it), and then move on to the first important part of the instance, The Library. (see map above).
Gathering the quests:
-  Into the Scarlet Monastery (elite) - Most important quest (given by Varimathras in the Undercity, in the Apothecarium area.)
-  Hearts of Zeal (elite) (given by Aponthecary Faranell in the Apothecarium, Undercity) Pre-requisite for this quest is Going, Going, Guano!, a quest involving the instance Razorfen Kraul.
-  Compendium of the Fallen (Elite) (given by Sage Truthseeker in Thunder bluff, you can find him on the lower rise, in the house connected to the bridge taking you to the Spirit rise).
Note: Undeads do not get this quest. (for lore reasons)
-  Test of Lore (elite) This is the follow up quest of a very long serie of quest, starting with  Test of Faith, given by Dorn Plainstalker, in the Thousand Needles, northeast of freewind post. It is up to you if you want to do this long quest or not.
-  In the name of the light Most important quest (given by Raleigh The Devout, in Hillsbrad Foothills, Southshore). This quest has pre-requisites: Starting with  Down the Scarlet Path (given by Brother Anton in Stormwind city)
-  Mythology of the Titans (given by Librarian Mae Paledust, in the city of Ironforge)
-  Rituals of Power (Elite) There is a mage only quest involving retrieving a book in the Library. The quest is given by Tabetha, in Dustwallow marsh, right in the middle of the zone, and a bit to the south. It is a follow up quest, you need to be at this point in your 'mage only' quest line before going to Scarlet Monastery.
Scarlet Monastery is located in the Northeastern part of Tirisfal Glades.
After going up a long corridor you will be in a large room with pillars in the middle, filled with scarlet denizens all around. Clear your way to the opposite side of this hall, and you will reach the 4 entrances to the instance. The two middle doors are locked, they give access to the Armory and The chapel, you can't access them yet. The blue portal on the left gives access to the Graveyard, the blue portal on the right gives access to the Library.
The Graveyard: (optional)
The Graveyard part of the instance is through the Left blue portal, as explained above. It is totally optional. If you go there and clear the first corrider to the first room, you will be in a torture room, and an easy mini-boss will be there, he doesn't drop anything worth it, but there is also a tortured prisoner there, who gives you a quest:
-  Vorrel's Revenge (Elite) (Horde only)
If you go to the end of the graveyard you will kill an easy named who drops blue loot sometimes, but really not worth it compared to what you can get in the other part of the instance. On the other hand, this part is easy and can be done by a low 30ish group.
Now on to the interesting stuff, to the library! Enter the blue portal to the right.
Group composition: lvl 35+ basic party. You need a tank, a healer (priest/druid), some crowd control against humanoid (Rogue / Mage / Warlock) and anything else.
The only real danger of this instance:
Runners. Every single mob (besides the hounds) in this instance runs away in fear when getting low on health. This is almost the only reason why parties can wipe there. So two things:
- Have someone on snare duty (by snare I mean movement slow effects such as Hamstring, concussive shot, etc, or even better, warlock's curse of recklessness).
- Always pull way back, so you have room for errors.
The first corridor is a mix of Scarlet Gallants, Scarlet Adepts (priest type, so be ready to interupt their heals), and Scarlet Beastmasters (+Hound pet).
It's easy if you follow the rules above. After clearing first corridor you will reach the Huntsman's Cloister. Clear it entirely, then go south to the room where Houndmaster Loksey awaits you.
Houndmaster Loksey deals quite a lot of damage for his level, so if your party is rather 35- than 35+, I suggest you take this fight seriously.
He is guarded by 3 hounds, which don't do nearly as much damage as Loksey does. If you have a druid, put one dog to sleep, if you have mage, sheep one, as for the last one it's up to you. Send the warlock or hunter pet on it, or even, ask the warlock to cast fear the whole fight. (if you cleared the previous room entirely, there's no risk in doing that)
Kill Loksey first, and then finish the easy dogs. Congratulations, you just finished 1/4 of the main quest.
Get moving fast though, because respawn rate is quite fast in Scarlet Monastery.
On the way toward the final boss of this part of the instance, you will meet new mobs, a bit higher in level than the rest: Scarlet Chaplain (priest type), Scarlet Monk (deals high melee damage, but low defense), Scarlet Diviner (casts fireball a lot, interrupt it).
You will finally reach the Athenaeum, where you will find the books you need to complete the Test of lore and Compendium of the fallen (Horde) and Mythology of the Titans (Alliance) as well as the mage quest Rituals of Power. Check the shelves at the spot shown on map. Also, if you have the quest Test of Lore, you will have to clear one of the little side rooms before reaching the Athenaeum, free world of warcraft the book is on a table inside of it. (see map)
At the end of the library, you will find Arcanist Doan(lvl 37 Elite), he casts the following spells:
- Arcane Explosion, it's an Area Effect spell, and he casts it a lot, so if you are not supposed to be meleeing him, stand away from it.
- AE Silence, he casts it from time to time, so make sure your casters are far away from him.
- Polymorph, sometimes he turns a group member into a sheep. If you have a Priest he can remove it with Dispel Magic, if you have a warlock, his Felhunter pet can remove it as well.
- Arcane Shield, he casts it once in the fight when you get a good chunk of his health down. He is immune to everything while this Shield is up, and it lasts about 10 seconds.
He is Immune to Stun, Silence, Shield bash, etc. But he is a caster and therefore doesn't have much Hitpoints, even though he is a boss.
He can drop one of the following items:
As well as the Mantle of Doan or the Robe of Doan, so-so green items.
In the back of Arcanist Doan's room, you will find a treasure box on the floor, open it, and you will aquire the key to the 2 last instance parts of the Scarlet Monastery.
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