When you arrive near the exterior, there are two ways to proceed. The first is through the rather obvious door, which will land you in Canterbury tunnels, and not the AntAgonizer's lair, in the last room there is a switch to open up to a stairway leading to the lair. The caverns are mostly empty, but contain a few ants to fight and a decent number of frag mines. Follow the caverns through to the end, and you'll arrive at the front of the AntAgonizer's lair.
Alternately, on the top of the hill that the door is embedded in, there's a grate which will drop you right into the back of the AntAgonizer's lair. However, the grate is locked and you will need a Lockpick skill of 50 to be able to pick the lock. A key exists, the AntAgonizer Lair key.
If you decide to travel through the tunnels rather than lockpicking your way directly into the AntAgonizer's lair, you'll come across a relatively empty set of tunnels filled with mines, a few ants, and the occasional trap.
The AntAgonizer can be found here sitting on her throne. If you walk up to her, she will confront you.
Among the jagged rocks on the hill above the door to the Canterbury tunnels, there is a triangular section of indented land between the trail and one of the boulders. The area is noticeable as having a discreetly blurrier texture than the rest of the pathway. Avoid falling into this indentation, as its geometry will effectively render the player unable to walk or jump, forcing a reload. As such, it is advisable to save before approaching the AntAgonizer's lair.
An easy way to discover the lair without the aid of non-player character's is to simply follow the Antagonizer after her confrontation with the Mechanist. If any of her ants survive they'll often get stuck outside the door, but still be labeled as friendly.
There is an unowned bed in the back which makes the lair a viable choice for player housing, as long as you don't mind the walk through the tunnels.
Near the unowned bed is some loot and a secret passage that leads out of the tunnel and back outside, making for a much quicker exit than going back through the tunnel.
ps3 The dialogue options to cause the AntAgonizer to give up her costume may not appear in the list of choices when speaking to AntAgonizer. This will result in the player having no choice but to kill her. [verified]
pcps3xbox360 There is a certain point on top of a rock which somehow considers the player to be under irradiated water. [verified]