This level occupies the map slot MAP29. For other maps which occupy this slot, see Category:MAP29.

Entity's Lair is the final area in the game Strife, accessed from the Alien Ship.

The starting room is a big room with a couple of dead ends, and a couple of hallways that house energy packs for the flamethrower and mauler. The Sigil door in the main room leads to another hallway which eventually ends at a huge arena, where the Entity is fought. To enter this large door, the player must have the fully completed Sigil in hand in order to open it.

Upon entering the room, one of two possible things will occur, depending on how you played the game and which path you chose when faced with the Oracle quest:

1. The player will hear Blackbird's voice, who acts as if she has been using the player to reach her own plateau of power via the Sigil, but as her lines close out, her voice morphs into that of the Entity itself, revealing the Entity can take on the voice of others, and Blackbird's true fate is unknown, or that she was the Entity itself. (This happens if the player killed Macil before the Oracle and didn't go to the factory where the cure to the virus can be found, thus this is the less desirable of the two positive outcomes.)
2. A voice, presumably the Entity, tells the player that even though he has crushed its Order, it will prevail and infect and twist the player to its will. (This happens if the player kills the Oracle before killing Macil, as Macil sends the player to the factory where the cure to the virus can be found, and this is the preferred of the positive outcomes.)

Two possible endings can be gotten at any time on this map. If the player dies while fighting the Entity, the bad ending is received. If the player kills the Entity, then depending on how the player went through the game, they will either receive one of the two better endings.