This expansion combines Portal narrator GLaDOS with the avuncular Entity narrator from previous Defense Grid games. The 8 new maps resemble the Aperture Science facilities but are structurally the same as previous Defense Grid maps, allowing construction of the same towers.
The plot for this series opens with the Entity happily welcoming GLaDOS as an aid against the aliens, before he is overwhelmed by her on the first map and only occasionally able to advise or help the player. This affects gameplay as GLaDOS revels in not only insulting and misleading the player with Portalesque comments, but in taking away towers, not allowing certain (or any!) towers to be built, or increasing the alien presence beyond what it possible to defend.