Liara is, by far, one of the most useful squad members Mass Effect 3 has to offer. With a complete biotic skill set, Liara is a powerful ally against armored, shielded and barriered foes alike. Dr. T'Soni can use Singularity, Warp, Stasis and Warp Ammo, all of which decimate all types of foes. Warp Ammo and Warp are powerful against armored or barriered enemies and Stasis stops foes dead in their tracks. Her most useful power, however, is Singularity, which makes foes float and dangle in vortex of dark energy.
Just don't ask her if her "hair tentacles" move.
