Threat: Very High
Attacks: Gunfire, cloak, melee attack, instant-kill
Description: Phantoms have a variety of attack modes. Most of the time, they will rush you head-on and engage in melee combat, slashing their swords in a wide area while doing acrobatics. While closing in, they will spam a moderate-range gunfire attack that VERY rapidly drains shields and health, and can quickly down a player in a few shots. Their swords inflict massive damage in a wide area and also inflict an unavoidable instant-kill animation that seems to be triggered at random if the Phantom gets within very close physical proximity to a player. In multiplayer, a Phantom can easily slaughter an entire team in close quarters if they are unprepared or ill equipped. After losing her barrier, she will often cloak and take cover near you.
Vanguards are the obvious choice to counter the Phantom, but the Vanguard player must be careful not to lose health during the battle, or else risk her instant kill. The best approach is to weaken her barrier by any means available before she can close to melee range, then use the Nova + Charge combo to stagger her and finish her off quickly with shotgun and heavy melee. Vanguard vs Phantom fights will mostly boil down to who can hit the other first with their most potent attack (the Phantom's sword frenzy vs Nova/Charge). In multiplayer, the presence of another player at a safe distance assisting the Vanguard with gunfire or powers can be the difference.
Infiltrators firing a sniper rifle from cloak can kill Phantoms with a single headshot. Maximized cloak duration is critical in this situation. A Phantom who does not "see" any player frequently will remain stationary and attempt to hide behind cover, often exposing all or part of their head, giving Infiltrators a golden opportunity to eliminate the threat with one pull of the trigger.