Forbidden Knowledge

Acquisition
Forbidden Knowledge is a quest acquired either from a letter, or by finding any Evil Tome (Act 2).

If not killed during Enemies Among Us, Idunna sends the letter:


 * Serah Hawke, 
 * Years past, I fell into wickedness and was swept up in the mad ambitions of the blood mage Tarohne. You spared my life at the Blooming Rose, and for many months, I wished you had killed me. But I found the Maker's Light in my deepest despair, and I now seek absolution.


 * Tarohne wrote many tomes containing dark secrets she learned from the Fade. She protected them with demons forged into their very bindings. You must find and destroy these tomes, lest others follow her dark path. I wish I could help you, but the templars never let me leave my cell. I can only send my prayers. 


 * -Idunna.

NOTE: You must destroy the first 5 tomes in order to finish the quest and access the last tome in Darktown.

Walkthrough
After entering an area with a tome, the map will show an arrow towards it. Be prepared to fight several packs of demons in each cave. This quest should be completed in the second act.


 * In Abandoned Thaig, the entrance (known as "Recently Opened Passage") is at the west end of Sundermount, in a corner left of the north-western exit, accessible only in Act II. The tome is found in the main room of the thaig next to the Nexus Golem (for the battle in this room, see "strategy" section in Abandoned Thaig page).
 * A cave at the east end of The Bone Pit (Inside the mine). Inside the location is called "Cave"
 * A cave in the northern middle parts of The Wounded Coast. It should be named "The Dank Cave" and is not marked on your map. Note that this cave is inaccessible later in the game.
 * In The Chantry, on a table from the southern stairs, second floor.
 * In the Viscount's Keep, eastern part on a table near the throne.

You can choose any of the following options when selecting a book:
 * (Destroy the book.)

+750 xp
 * (Read the book.)
 * (Accept the book's deal.)

Item received: Greater Tome of the Mortal Vessel +2 attribute points for Hawke
 * (Take the book.)

NOTE: to get the plus 5 approval you must first select read the book and then take the book. (Take the book.) Item received: Book of Forbidden Lore (trash item) Choosing any of these options will cause several demons and abominations to appear and attack.

NOTE: Reading and accepting the book's deal will give you +2 attribute points, but this will only happen once, any books read after this will not give any attribute bonuses. Also, taking or reading any of the books makes the player unable to complete the quest, and the quest will remain in your journal. However, if you ONLY read the last book (named The Fell Grimoire) you will complete the quest, fight Xebenkeck and get 2+ attribute points.

NOTE: You will only receive when you read or take the first tome. Each tome thereafter you will receive no status change.

However, you will receive for every tome you choose to destroy, unless you have max out Merrill frindship in that case after destroying the book there will be no impact on Approval.

After destroying the five Evil Tomes, your Journal will update, and you will get information on The Fell Grimoire. It can be found in The Forgotten Lair, which is an area in Darktown next to the entrance. Note that you may come across a locked door and will need a Rogue to unlock it, in the Forgotten Lair. Inside the cave there are several traps, some of them are capable of killing most members of your party rather quickly so watch out for them - there are spaces where you can walk without triggering them. (A good tactic is to use a ranged companion to pull any enemies back to a cleared area and take them down before moving to clear/go around traps. If you can't avoid the traps, position each person where they will not take damage - usually on the extreme edges of the area or path -  and hold your party until the traps stop firing, then continue.)

After destroying the Grimoire you will meet one of the most dangerous bosses in the game, Xebenkeck, a powerful Desire Demon. The boss itself is not very hard but she will summon hordes of Rage Demons and Abominations, as well as a Revenant in the second wave. See Xebenkeck (strategy) for tips on how to defeat it.

Result
The Fell Grimoire and Tarohne's tomes were destroyed.

Rewards
Voracity can be found on the body of Xebenkeck and you are rewarded with the achievement "Exorcist" after killing all the creatures inside.

Note

 * If you choose to take the books, you can sell them each 86. 5 books = 4 38.
 * If you are seeking the Supplier achievement, be sure to grab the Raw Lyrium from the cave on The Wounded Coast and the Corrupted Lyrium in the cave in The Bone Pit

Console command

 * For PC only: There is a possible work-around to still acquire the Fell Grimoire, as not doing so is very disappointing, using runscript zz_lgt_debug in console. Choose Act 2, More Plots, and choose Forbidden Knowledge.


 * For PC only: It is possible to complete this quest even if you have read one of the books before. To do so you need to use gffeditor to edit your saved games. Advised to create new save before you edit.


 * First of all, go to the Hanged Man Inn(or anyplace else except your own home) with the party you want to fight with. Then open the saved game you want to edit with gffeditor(i.e. savegame.da; It can be found in my documents\BioWare\Dragon Age 2\Characters\Garrett\Saves\Slot_6)


 * Next go to SAVEGAME_CAMPAIGN and there find CAMPAIGN_CIF_ENTRY_AREA_LIST and CAMPAIGN_CIF_ENTRY_AREA. Now you need to edit both of these to-> lgt231ar_tome_final (old one is dae221ar_player_home_nt if you are in your home in act 2) after editing each, press save from bottom left corner and then file -> save as -> overwrite the save your editing.


 * If you find yourself stuck in a wall when loading your save, either move towards the stairs inside the bar before editing your save, or simply set the values of CAMPAIGN_CIF_ENTRY_POSITION to :
 * for a : 2.51166415215
 * for b : 6.18907737732
 * for c : 0.100000202656


 * A second alternative to being stuck, is going to the entrance, and as soon as one of your companions walk-walks through, select him and your whole team should be properly located in the corridor.