Carrington Institute: Defense is the fifteenth level in Perfect Dark. This the only mission where you can get friendly assistants in the form of Carrington Institute guards. They make use of the AR54s against the attackers, which compose of shielded DataDyne shock troopers packing K7 Avengers. Thankfully Joanna starts with an AR34 (Which she 'borrowed') so it gives you some chance against the enemy. Because of the endlessly respawning enemies, all of which carring K7 Avengers, and the brutal time limits, this is generally considered to be the hardest mission in Perfect Dark.