Arrival was originally the last major DLC, and it’s about a missing, deep cover agent in Batarian space. The Legendary edition already has it, so it doesn’t need to be purchased.
Choice: Complete Arrival or not
Completing Arrival will let you go to the Bahak system in the Viper Nebular, and you’ll also get three upgrades: Heavy Weapon Ammo, Medi-Gel Capacity, and Heavy Skin Weave.
By completing the Arrival assignment, you’ll begin Mass Effect 3 in alliance custody, and the reason for this will be due to the destruction of the Alpha Relay. Also, if Balak survived in Mass Effect 1, it’ll give him another reason to hate you.
Don’t Complete Arrival
By not completing the Arrival Assignment, you’ll be held in custody for working with Cerberus during Mass Effect 2. Also, the War Asset: Alliance 103rd Marine Division will have its strength reduced by fifty points due to dying in an incident that you should’ve been a part of.