Black Market is the first DLC for Avorion:

Black markets
With the DLC, black markets open on the stations in Avorion. These are not immediately available to every player. Enterprising space adventurers have to attract the attention of the alternative markets in order to receive an invitation, but... the effort is worth it. On the black markets, the players get better offers for their goods and most importantly: No annoying questions are asked. ­

Docking
With the help of the docking mechanism, it is possible in Avorion for the first time to dock the players' own ships, stations or freight containers to their spaceship. This feature is not intended for warlike actions and stealing foreign ships. However, players and NPCs still have to defend their cargo, because containers can be stolen. Docking will be available for all players as a free update on the release day of “Black Market”

Steam: https://store.steampowered.com/app/1357160/Avorion__Black_Market/