After completing a main plot world and leaving the system, Shepard will receive a communiqué from Nassana Dantius upon entering a new star system. Go back to the Embassy Lounge on the Presidium and speak with her for details.
Alternatively, you can get information on the mercenaries from Yaroslev Tartakovsky's log on Noveria. These are to be found by hacking a terminal at Peak 15, upstairs in a corner of the cafeteria (where you first encounter the rachni). Note, however, that this will only be present if Noveria is the first world which you visit.
It is also possible to go directly to Sharjila in the Macedon system before being made aware of the mission - or after receiving the mission but before returning to the Citadel to speak with Nassana - with similar results. Afterwards you can still speak with Nassana. This can be done at any point after acquiring the SSV Normandy.
Attempting this mission at low level will result in a long difficult war of attrition. You'll be better off saving this one until level 30 or higher, at which point whichever squad configuration you prefer should serve you well.
Nassana will tell you that a group of mercenaries attacked a freighter where her sister was a crew member. However they since kidnapped her for ransom money, as their family is prestigious and well known. Nassana says that she paid the ransom to the required account but that her sister was not released. As she is an important ambassador, by Citadel law, Nassana should have reported the situation to C-Sec. She explains that if her actions were discovered, she would lose everything. Having already found the mercenary location by tracking the ransom money she had paid, she asks for Shepard's help. Head to Sharjila to rescue Dahlia.
Dealing with the Pirates Edit
Upon landing on Sharjila, you will notice that it is a pressure hazard, so plan to limit your time outside the Mako. The stronghold is directly north of the Mako's landing site, and heavily defended. In four towers are Pirate Snipers and on the ground are a further five Pirates, including a krogan, and another Sniper. Deal with the krogan and the snipers first, preferably staying inside the Mako while snipers are about to avoid getting one-shotted by their Assassination ability, then switch to the regular grunt pirates. When they are all down, head into the stronghold. Warning: Keep an eye on the Level 1 Hazard bar if you're fighting outside the Mako; Pirates can take a long time to kill so it's easy to lose track.
Once inside, it is recommended that you save your game because there are a further seven Pirates, another two Snipers, one on the main floor, and a second on the upper floor catwalk, and their leader, the Asari Slaver. The wall directly in front of the door will provide some good cover, so use it. There is another krogan pirate in the main room as well, and like all krogan, can regenerate unless killed in the air. This battle can be tough especially if you let any of the pirates get behind you, so don't let that happen. The cover in front of the door is the best spot if you can hold it, but don't be afraid to backpedal into the entry room if you need to. If some enemies take cover hear opposite the entry door, there is a fuel tank that you can use to either severely wound, if not kill them. Using the Overload ability works great as it amplifies the explosion.
Sometimes the Asari Slaver, doesn't come down from the second floor right way, neither does the other sniper, but they will come down eventually. Just keep your cool and focus on taking out the enemies as quickly as possible. Once they are all down, there are some crates around that you can grab. There is a medical kit on top of one of the crates near the door, you'll have to mount another crate to get it, an upgrade kit about mid-way along the right wall, and three crates and a medical station in the room on the ground floor.
When you get to the second floor, the only loot is in the room. Inside are a Hardened Storage Locker, a Hardened Wall Safe, and a malfunctioning object. There is also a desk in the upper room, investigate it to learn that Nassana deceived you, the Asari Slaver is actually her sister! With the evidence in hand, leave and return to the Citadel to confront Nassana with the evidence.
Dealing with Nassana Edit
When you get back to the Citadel, meet with Nassana again to confront her with the evidence, or tell her about her sister's fate. With Charm or Intimidate you can get her to grant you access to 'prototype asari mods' in addition to your payment. To acquire these new mods, you can purchase the Armali Council License from Commander Rentola in Virmire: Landing Zone.
- Choosing "I've got a better deal." (requires Charm skill level 3) allows you to buy the Armali License. You do not get Morality points for this option.
- Choosing "Don't bother." gets you 2 Paragon points and XP, but no Armali License.
- Choosing "Fair enough." gets you no Morality points or license, just the base XP and credit reward.
- Choosing "It better be." gets you 2 Renegade points and XP, but no Armali License.
- Choosing "Credits won't cut it." (requires Intimidate skill level 4) allows you to buy the Armali License. You do not get Morality points for this option.
Note: it is possible to kill Dahlia without speaking to Nassana first. Doing so will result in a different conversation with Nassana afterward: she will lament not being able to manipulate Shepard as she had originally planned, but she will reward the Commander anyway.
Mass Effect 2 Consequences Edit
During Thane's recruitment mission, Shepard will remember how Nassana manipulated them into killing her sister while speaking with Seryna. After the squad fights their way through Nassana's guards and confronts her in the penthouse, she will say that Shepard is now finishing the job that was started with her sister, and now Shepard is here for her.