To get this achievement, you need to deliver the artifact at the drop zone while four or more enemies are within ten feet. This is closer than it sounds, just having enemies in the general area isn't good enough. The catch here is that you can't take any damage from the time you pick up the artifact to the time you deliver it.
This is a very difficult achievement to get legit. I managed to pull this off twice, but both times the game lagged out shortly after. Quite possible that the lag was a significant contributing factor. The best advice I can offer is to go in with a group and let them get ahead of you in hopes of distracting the enemies. Trolls work best for drawing fire.
It's also possible that if you do take damage, you can still net the achievement by dropping the artifact and picking it back up just before scoring. I cannot confirm this, however.
Obviously, the easiest solution to this is to boost it with people who are cooperating. Remember that boosting can be done in a private match as long as you have at least eight human players in the game. If you've got less, it's not going to count.