Nice work - you have already found some of Twirl's guys, lying dead! There are 20 more men remaining (when you reach the Gate, Twirl might even mention that he has already lost four men during the breakthrough) - looks like the Drones and tripmines have did their job. However, compared to Twirl, and his 23 chums, 4 casualties are mighty few.
To enter the rock lair, you have two options here - an easy one, which requires careful planning and finesse, and a much harder, which requires firepower (using the fallen Taskforce members' weapons makes it easier).
- The entrance is barricaded with tripmines,right? And there are Acolytes inside that small rock stronghold, right? Just get their attention, and then....hehehe
- There is a second
Artifact of Invulnerability hidden in the park. Look for it near an angel statue at the monolith in the center. Watch out for detestable Drones. When you grab this Artifact, you'll need to scurry back to the fortress and the tripmines will harmlessly explode upon entering. Also don't worry if you do not receive any "you have found a secret" message first - you'll get it once you grab the 9mm clip near the fissure gate.
And remember - Twirl and his friends have picked off most attackers on their way (you can easily guess what route did they choose), but the sounds of the firefight lured more enemies nearby from the surroundings of the falanster, where they were scouting - especially Drones. Using your Stealth rifle, you can easily pick off the Drones - or Sabrine MK3. I don't recommend Knife fury, but it works nice against Acolytes in case of ammunition shortage.