Pirates have managed to capture a 104-gun ship of the line. Fortunately the vessel was heavily damaged in the process and is neither seaworthy nor fully manned at the moment. Before that can happen, you have to destroy her. And better bring allies, because that ship will still be fully armed.
- Sink the 104-Gun Ship
This is a GROUP mission and rather infamous for a variety of reasons: for one thing, there will be an ambush during the mission, when six enemy ships will appear and attack you; and also, it takes place on an unusually small map, making it very difficult to evade these enemy ships and get out of their range to regenerate your ship's structure. Bringing a group is strongly recommended.
At first, the number of opponents will seem manageable: there will be the already heavily damaged 104-gun SoL you have to sink (level 50), which will be under the protection of two level 15 forts. There will also be two guard ships roaming the area (both around level 17-19, same as the ambush fleet spawning later on).
It is recommended to take out the two guards without getting in range of either the forts or the SoL (because this will trigger the ambush). Usually they will come for you straight away, but since the map is so small, you will still need to be careful not to maneuver too close to the stationary opponent near the shore.
Once the escorts are down, wait and heal up before attacking the SoL. Especially if you're trying this mission solo, you will want to give yourself as much room to maneuver as possible, and also use the terrain to your advantage. There is a large island in the middle of the map (don't stray to the west of it, or you'll be firmly in range of both forts and the SoL), and a small island in the NE corner. You can hide behind the latter one and in this way avoid fire from all but two or three enemies at the same time (this will however reduce your maneuvering space).
There are currently conflicting reports if killing the ambush ships is required for the mission to succeed or not (with most of the answers tending towards "yes" - see the link below). This does not show up in the mission objectives at any point however, but to be on the safe side, you should assume that you have to take them out as well. Therefore it would be better to only sail into the SoL's range for a short time and then retreat to engage the ambush ships.