Best Served Cold is received via a letter from First Enchanter Orsino after finding the three mages for Knight-Commander Meredith. If you sided with the Templars at the beginning of Act 3, this quest will alternatively be received from Knight-Commander Meredith.
After you get the quest, go to Hightown at night and head to the Hightown estates neighborhood.
There, a battle will automatically begin when you enter the area near to where you need to be. You'll need to defeat a group of Templars and 5-6 Mages to beat them all. Afterwards loot the bodies to find a note that will instruct you to head to the Docks (and an armor upgrade for Sebastian).
Go to the Docks and follow the arrow to your destination. You may encounter one or several groups of Slave Hunters, otherwise head into the Warehouse. Once there open the door and you'll encounter another cut-scene before you have to battle another group of Templars and Mages. There are two standard traps (requiring 20 cunning to disarm) in the main room, one on the eastern side and one on the western side.
Keran may be here if he lived and is with the Templars; he will tell you that someone close to you has been kidnapped by the rebels and that they have been taken to a hideout on the Wounded Coast. At this point you have the choice of
- Turning him in to the Knight-Commander Merrill: rivalry (+10), Varric: rivalry (+5), Aveline: friendship (+5).
- Killing him, If you have Merrill in your party and you choose to kill him, she'll say not to, that he is not responsible. If you decide to kill him still it will result in Merrill: rivalry (+5). If Sebastian is in your party, he protests that Keran merely got in over his head, something that doesn't merit death; choosing to kill him results in Sebastian: rivalry (+10).
Note: If it's your love interest that is supposed to be taken, Keran will describe them- however you will still be able to select them and go to the Wounded Coast.
Loot the area, there is a complex (30 cunning, 150xp) chest to the right of the entrance and the Blade of Mercy.
Exit to the Docks and head to the Wounded Coast. Take the low path and head south towards the Ruins.
Fight a small group of Templars and Mages on the way. A cut-scene will then occur where Samson will approach you; state the mages must be stopped for Merrill: rivalry (+15), Fenris: friendship (+10), Sebastian: friendship (+5). After the scene continue down the path until you reach the main group of Templars/Mages. They are being led by the templar Thrask, who will implore you to side with them against Meredith. Behind him, whoever was taken hostage will be lying on the ground, unconscious. Choosing the aggressive option when speaking to Grace nets Sebastian: rivalry (+5), while the diplomatic response gives Sebastian: friendship (+5). Fenris: rivalry (+10), Sebastian: rivalry (+5), Anders: friendship (+10) if you speak in support of the mages. Whether you sent her to the Circle, or let her go during the quest Act of Mercy, one of Thrask's companions will be the apostate mage Grace; she will call for the hostage to be killed and then turn on Hawke, killing Thrask in the process. Note that choosing the aggressive option when speaking to Grace nets Sebastian: rivalry (+5), while the diplomatic response gives Sebastian: friendship (+5). During this battle, Grace herself is easily taken down, but becomes a Pride Abomination upon death. After the battle, Samson will return with Cullen. As with Keran earlier in this quest, you will have the opportunity to decide the fate of Alain and Samson.
After the fight talk to Cullen to decide the fate of the surrendering mages and rogue templars. Knight-Captain Cullen will permit Samson to become a Templar again if Hawke requests that he give him another chance. Hawke can also ask Cullen to be merciful to Alain and the other mages who are arrested.
Note: Mage Hunter and Arcane Defender Achievement: This is your final chance to side with either the Templars or Mages. During your conversation with Cullen: (Side with Templar) Say "Alain was working with Grace." and select "Give Samson another chance." Or Say "Kill them all". (Side with mage) Say merciful to Alain and others. The achievement will not pop up until you report back to either Meredith/Orsino to end the Quest (providing you have sided with the same faction 4 times previously).
When you talk to Samson and defend the mages, you get Varric: friendship (+10), Merrill: friendship (+10), Fenris: rivalry (+10), Sebastian: rivalry (+5). If you go against the mages, you get Fenris: friendship (+10), Sebastian: friendship (+5).
Once you return to the Gallows Courtyard, you may speak to Cullen to discover how your recommendation decided the fate of the surviving conspirators.
Return to Orsino/Meredith to complete the quest.
If you tell Meredith that she is paranoid: Aveline: friendship (+5) or if you tell her that Orsino is blameless and name names: Aveline: rivalry (+5) (perhaps more as my rivalry with Aveline became maxed at this point)
Afterwards, if you return to Hawke's Estate, you will find a letter from either Meredith or Orsino that pertains to the quest The Last Straw.
Bethany/Carver will be kidnapped if they are alive. It does not matter if they are with the Mages/Templars or the Grey Wardens.
If Bethany/Carver is dead, then your love interest will be kidnapped. However, they will only be taken if they are not in your party when you travel to the Wounded Coast.
If Bethany/Carver is dead and your love interest is in your party (or you don't have one), the companion with the highest friendship score who is not in your party at the time will be kidnapped.
Sebastian cannot be taken as a hostage.
- Hood of the Champion
Requires: 31 magic
+2 mana/stamina regeneration
+58 attack (Mage) or Helm of the Champion
Requires: 31 dexterity
+3% critical chance
+6% critical damage
Bonus to lockpicking (Rogue) or Helm of the Champion
Requires: 31 strength
+3% critical chance (Warrior) - looted from Grace
- The Tiger's Tail
Damage: 39 fire damage
(53 per second)
+6% critical chance
+15% critical damage - looted from Grace
- Protection of the Faith
Companion armor upgrade
Extra rune slot (armor upgrade for Sebastian found at Hightown estate encounter)
- Sigil of the Mage Underground
Companion armor upgrade
Extra rune slot (armor upgrade for Anders found in the Dock's warehouse)
- Three Wolf Boon (found after the fight on one of the corpses in the Dock's warehouse)
- Blade of Mercy (a gift for Fenris)
- 1200 XP (quest completion)
- Cumberland Circle Robes
Requires: 28 magic
+5 mana/stamina regeneration rate
+25% healing by this character from Orsino
- Hearth Shield
Requires: Weapon and Shield
+4 health regeneration rate
+19% healing to this character from Meredith
- When encountering the mages in Hightown (night) the corpse you are supposed to loot might disappear. Loading an earlier save is the only way to proceed with this quest.
- After encountering the mages in the warehouse at the Docks (night), return to Hawke's estate and leave. Even if Isabela is kidnapped, you will still be able to select her for your party. If you bring her to the Wounded Coast, this leads to an amusing scene where there are two Isabelas. One unconscious on the ground and the other fighting.
- If Anders is kidnapped, you may still be able to use him in your party.
- If Bethany or Carver joined the Grey Wardens and is kidnapped, she/he may appear wearing their Circle outfit/Templar outfit instead of their Warden Uniform. Graphic based only, does not affect/change game decisions (Confirmed on all consoles).
- If Keran was forced out of the Templars at the end of Enemies Within, he will still be one of the Templar Conspirators. The dialogue will be the same regardless of the earlier decision.
- On pc 1.03, this is not the case; Keran states he cannot stand by idly in good conscience despite having been discharged.
- If Samson is made a Templar again, he will still appear in Lowtown(night) begging.
- If Death Syphon is active, it is possible that Grace's corpse will disappear and therefore not be able to be looted.
- The name of the quest takes its name from the common expression dating from at least "Don Quixote"  that revenge is best served cold.