Banshee

Banshees are synthetic-organic creatures derived from asari and mutated by Reaper technology. Frighteningly intelligent, Banshees are advanced pressure units usually found leading a Reaper strike force.

Banshees are created specifically from asari with active or latent predispositions to becoming Ardat-Yakshi.

Capabilities
Offensive

Banshees can charge their enemies (similar to a Biotic Charge) however, this charge only has a range of about five meters, so the Banshee moves quickly using a series of biotic "hops". They also have the ability to grab people and subsequently impale them with their hands, resulting in instant death. Sometimes they will stand still and briefly appear to charge up, after which they will scream and release a damaging Nova over a surprisingly large area. Finally, they throw powerful biotic projectiles (similar to Reave) that move slowly but track their target. If one gets hit by the projectile, weaker shields are instantaneously destroyed and up to two health blocks are drained over time. Stronger shields, or defensive bonuses can negate health damage. Further, the drain can be interrupted by any shield/barrier restoring power (i.e. Geth turret's Shield Restore and Energy Drain).

Defensive

Banshees possess substantial biotic powers, and can use their biotics to create barriers to protect allies. They can also use their charge ability to move quickly and unpredictably, which can make them very difficult to hit at range. They have strong barriers and very strong armor, putting them almost on par with Atlas Mechs in durability.

Tactics

 * Besides its deadly melee and shield depleting Nova ability, even a single Banshee will always have other faster moving units - if not heavy hitters - accompany her, so be prepared to fight a mobile battle and aware of your surroundings so you won't be swarmed or flanked by other Reaper units;
 * Especially in Multiplayer missions, in later waves it is common to have at least one Brute in the wave with a Banshee, which is a very dangerous combination, so be aware of your surroundings thus avoid being boxed in.
 * When damaged after their barriers are knocked down, Banshees will sometimes drop to their knees and scream to regenerate. This scream does no damage, and is an opportunity to get in close for melee or shotgun attacks. This is risky however, as the banshee can grab you and kill you instantly.
 * While no less deadly, the Banshee's instant kill is the slowest to take effect. It can be interrupted (and the victim saved) if the Banshee is staggered by incoming damage (especially strong attacks like a sniper rifle shot from Tactical Cloak or Sticky Grenades), or killed.
 * Do not ignore the Banshee's ranged attack. While the biotic projectile can be dodged with some practice and the right timing (or sufficient cover), it is almost guaranteed to take down all but the strongest shields on impact, then afterwards take down at least bar of health. This can spell instant (if delayed) death if you're down to your last bar.
 * Despite being humanoid, the Banshee is immune to headshots, and does not take extra damage from them. Instead of the head, aim for the bigger target that is her bloated belly.
 * Classes that chiefly uses powers (Engineers/Adepts) in Multiplayer may consider keeping the Cobra Missile Launcher equipped when engaging Banshees to reliably save squadmates if they get grabbed.
 * It's important to note that, unlike in Mass Effect 2, Overload does more damage to barriers than Warp. Of particular note is the Rank 6 evolution of Overload that doubles its damage to shields and barriers. Therefore, all squadmates who can use Overload should concentrate it on the banshee to remove her barrier. After the barrier is depleted, Warp is better for wearing down the armor.
 * In Single player, it takes a tremendous amount of damage from squadmates' attack to dislodge a Banshee's melee grab. Given the small window of time it takes for the Banshee to execute the melee-kill, it is wise to avoid it altogether.
 * In single player on Insanity, the scream will remove all your shielding. For Vanguards, this can be avoided with a well-timed Biotic Charge (roll away immediately after) or Nova just as the Banshee kneels down.
 * It can be an efficient measure to use your squadmates' powers combined with yours to kill a Banshee. For instance choosing such powers as Reave, Dark Channel and Warp to take down her barrier and then shred her with an assault rifle. Might be risky, though acting fast and using squadmates' powers can finish her rather fast.
 * Be wary as some powers will never be able to affect Banshees due to their lack of a health bar, meaning they are always protected. Singularity, Pull and Stasis can't affect a banshee and will not leave an effect to be detonated on a banshee.
 * Be wary about sticking to cover. They can rapidly close distance and grab you, which is normally an instant kill.
 * A Vanguard can successfully use Biotic Charge on a Banshee, but it requires great caution. The Vanguard should immediately dive away from the Banshee to avoid its instant-kill melee attack.  This can be a useful tactic, however, if a squadmate uses Warp on the Banshee beforehand, as the Charge will detonate Warp for substantial additional damage.  The detonation will also stagger the Banshee, giving an extra fraction of a second to escape melee range.
 * After unleashing the biotic Nova attack, the Banshee will no longer be glowing. At this state, it is unable to either perform another Nova or teleport, making it the most opportune time to attack.
 * In multiplayer, the most effective tactic in dealing with a Banshee is to outright leave her alone and wipe out all other enemies first, most notably the ones that shoot at you. It is effective to imagine the Banshee as a moving grenade: as long as you have a good distance, it can't really do any lethal damage. Husks should take priority; if they grab you, it gives the Banshee the opportunity to instant kill you. Ravagers should take next priority; they do the most damage in a single volley. Marauders and Cannibals should follow afterward. If you follow this strategy, you'll have an easier time surviving.
 * Banshees have the highest chance to do an instant-kill grab when they are charging or glowing. Once they stop glowing, it's (relatively) safe to get closer without fear of getting grabbed. Once the Banshee starts screaming again, run away to a safe distance.

Morinth
If in Mass Effect 2 the player spared Morinth and killed Samara, then Morinth will appear in the mission Priority: Earth as a Banshee. She will not behave any differently from any other Banshee and must be killed as normal.

Trivia

 * In The Art of the Mass Effect Universe and The Art of Mass Effect 3, Banshees are incorrectly stated to be asari matriarchs, instead of asari with Ardat-Yakshi potential.
 * The Banshee is a female fairy or spirit from Irish folklore, whose wails are said to be an omen of death. Similar creatures appear in Scottish, Welsh, and Norse stories.