Marek and Lothander

The party is poisoned by an Iron Throne assassin named Marek and must find an antidote in ten days or die. His partner, Lothander, offers to help if you find a way to free him of his geas.
==Acquisition==
The "pre-quest" begins when the party is approached by Marek and Lothander in the eastern section of Northeast Baldur's Gate district. Marek tells them to leave or there will be dire consequences. What the protagonist replies to him has no effect on the outcome of the quest. However, if Marek is attacked and killed there, then he can never poison the party and the quest is avoided.
The actual quest begins when the protagonist meets Lothander in the marketplace in the district of Central Baldur's Gate. He will inform the party that they were poisoned while they slept and they will all die in ten days. At this point the ten day quest timer has just begun and the Marek and Lothander quest will be entered in the quest section of your Journal (see below).
== A slight hope ==
Lothander tells the party he has the antidote but he will only give it to them if they will help to release him from a geas that binds him to the Iron Throne's service. If the party tells him "No" he leaves, and they will not be able to talk to him again, resulting in their death from poisoning later on, which cannot be cured and ends the game. Killing him or pick pocketing him will also result in death as the cure he has on him is fake. If the player agrees to help him he leads the player to the Diviner who he thinks can tell them how to break his geas. It costs 50 gold to get a reading for Lothander. The player can refuse but, again, it only results in the party's death.
The Diviner tells the party that only the high priestess of Umberlee can break the geas. When they inform Lothander of this, he tells them to meet him at the Blade and Stars Inn when they have found a way to break the geas. The temple of Umberlee (Labeled 'Water Queen's House') is located near the waterfront docks in the district of South Baldur's Gate.
Once inside the temple, speak to one of the priestesses and ask to see the high priestess, Jalantha Mistmyr. The party will need to bribe the priestess with 50 gold to see Jalantha. She will tell them to wait, and after a few seconds the high priestess comes to speak with the party. She promises to help them break the geas if they will acquire the Tome of Understanding for her. It can be obtained from Chanthalas Ulbright, who is in the Temple of Tymora (otherwise known as 'The Lady's Hall'), located in the district of West Baldur's Gate. Alternatively, Jalantha can be killed for the scroll, however this will interfere with other quests involving her (see Tremain's Son). Alternatively, you can pickpocket the Geas Removal Scroll and a Sphene Gem from Jalantha. You should still go and get the Tome of Understanding, but it will save you returning to Jalantha.
== Retrieving the Tome of Understanding ==
Once inside the Lady's Hall, speak to Chanthalas Ulbright with your character who has the highest charisma. Tell him the party needs the Tome of Understanding. Ulbright will ask why he should give it up. If the party has at least 500 gold you will be able to offer it to him as payment, which he will say is desperation enough and will simply give you the book. Alternatively you can tell him it is a matter of life and death. If the party member speaking to him has a high enough reaction score he will give you the book, otherwise he may refuse. Failing all of these, he may be pickpocketed or killed for the book (with loss of reputation).
Regardless of method, once the party has the book, return to the Water Queen's House and give the book to Jalantha. She will give the player a scroll in return which will break Lothander's geas.
== Returning to Lothander and finding Marek ==
Meet Lothander at the Blade and Stars. The inn is located in the district of Southeast Baldur's Gate in the northwest corner of the local map. Lothander is on the second floor of the inn standing with a large group of Commoners. Once the player gives him the scroll, he gives the player a
* potion of antidote
* Lothander's Potion of Antidote
and tells them where they can find Marek who has the “other half” of the antidote. The potion he gave the player is useless as it is only a common potion of antidote. Marek is the only one with the real antidote, however you get for freeing Lothander of his geas.
The player can find Marek in the Blushing Mermaid. He will only appear there after Lothander tells the player he is there. It is impossible to find him without helping Lothander. The Blushing Mermaid is in the district of Northeast Baldur's Gate on the western side of the local map. It has a full color picture of a mermaid on the side with a blue background.
Marek is on the second floor. When the player speaks to him he will attack the party. He may be charmed before or after initiating dialogue to give the antidote without a fight. 
* Upon talking to Marek the party is healed and receives 10,000 XP. If for whatever reason talking to him isn't possible, going through the dialogues with Tethtoril in Candlekeep will remove the poison. The player won't be told about it and will gain no XP.
* After the party kills Marek a special antidote can be retrieved from his body. This is a potion with 10 uses, however, once the main character drinks it no further action needs to be taken. Finishing the quest by drinking the potion rewards the party with 10000 XP.
== Journal ==
The first encounter with Marek and Lothander is recorded as an untitled entry in the Journal section of the Journal.
Journal entries appear in the Quest section under the heading Marek and Lothander beginning with Lothander's request—and offer— when he approaches the party in the marketplace in Central Baldur's Gate.
Agree to help Lothander with his geas:
After talking to the seer:
Diplomatic option #2: