Story: Previously mission was very difficulty and many soldiers died. HQ send new squadron with more soldiers and better equipment. Also few npc return to complex and you found new rooms there.
Most important change is new weapon: UA 571-C Sentry Gun, it will fix problem of respawning aliens. After deploy you can put it back to box (just click it until turn to box again) and later use to secure other corridor. This is actualy best weapon in DM ever.
There is 9 new champions (soldiers and npc), several new items, music soundtrack, few changes in interface, new scenery and more places to explore, some details altered or balanced.
