Story related trophy, but it is missable.
This occurs in Kirkwall after you gain entry to the city. You will meet a rogue named Varric, and his brother Bertrand. Speaking with Varric and Bertrand you learn that they are planning an expedition into the deep roads and Varric offers you the chance to become a partner in this expedition.
There is a twist though, Varric and Bertrand request you put forth 50 soveriengs (gold pieces) to become a partner in the expedition. You can earn money by killing creatures, completing quests, and selling loot. It may seem like a lot of money, but you can get up to the required 50 pretty quickly.
Once your at the required 50 gold pieces, you have to go back to Hightown and locate Bertrand and then give him your 50 gold pieces, and you have yourself another trophy.
MISSABLE PART: There is another Dwarf named Dougal will send you a letter at your house to meet him at night in Lowtown I believe. Upon arriving there he will tell you that Bartrand wouldn't let him come on the expedition, but asks you to get him into the expedition. IF YOU DO THIS you will not get your trophy.