Tela Vasir (enemy)

Tela Vasir is an asari Spectre revealed to be an agent of the Shadow Broker. She leads Commander Shepard and Liara T'Soni into an action-packed chase around Illium's skyways, ultimately crashing into Hotel Azure. Bleeding badly, she doesn't limp far before Shepard and company catch up with her. Taking a hostage doesn't help her much, so she faces off against Shepard's team.

Her wounds eventually take a toll on her and she succumbs to her injuries after a protracted battle.

Capabilities
Offensive

Tela is armed with a M-15 Vindicator and will use Shockwave to dislodge you from cover while inflicting minor damage. She can summon reinforcements consisting of Rocket Drones and Shadow Broker Engineers. If you are too close when she comes out of a Charge, she can also inflict damage and knock Shepard off guard. She also has a powerful charge-type attack that causes major damage in a wide radius around her and knocks anyone caught in it off guard, though it has an extensive charge time that allows Shepard to get out of range.

Defensive

Tela's barrier and armor are extraordinarily strong and she will use Charge to move around the battlefield many times.

Tactics
General Tactics
 * Tela is arguably one of the hardest enemies in the game. She will try to keep some distance from you to use her assault rifle. Engaging her at close range is a good idea, since she doesn't have any close range attacks, just watch out for when she Charges. Once significant damage has been done to her barrier, she will exit the area and summon a squad of two Engineers and two Rocket Drones on you. She will do this again once enough damage has been done to her armor. She can knock you out of cover with a Shockwave, and her Charge can stun you, so be careful about engaging at range. Once her armor is down, hit her with a biotic Pull or Liara's Singularity and finish her off; falling off the edge of the battlefield for any reason will instantly kill her, saving the trouble of having to wear down her health.
 * Liara's Stasis is a good ability since it can stun Vasir even if her protection is still up, and turns her into a sitting duck once it wears off. If you use Stasis just before Vasir charges down after a wave, the resulting ragdoll will (usually) fall backwards instead of off the ledge. This causes the next wave to start sooner than normal and, after the final wave, will end the battle without having to bring down her health. This method isn't always possible, due to the line-of-sight requirement to use Stasis. To keep her in sight, try staying in the center of the map below where she charges from after every wave.
 * Tela seems to be more vulnerable to powers during her biotic attack's charge time, so unleash squad powers on her for greater damage. Hitting Vasir with two or more powers will also prevent her from using this Charge attack against Shepard, which could save you some time.
 * Heavy weapons like the Cain will not destroy her outright, it will just lower her barriers.
 * Because she frequently uses Charge, it can be difficult to target her for more than a couple seconds before she moves out of your line of sight. Using an ability or weapon that can track moving targets, like Warp, can be helpful.
 * Once her defenses are removed, Tela is susceptible to Dominate and can be kept immobile for the remainder of the fight by using that power.
 * Also, you could use any biotic abilities such as Charge or Shockwave, to knock Vasir off the edge of the map, instantly ending the boss fight.

Class Specific Tactics
 * If you are a Vanguard, a good tactic is to somehow strip her out of her barrier, then equip a shotgun and Incendiary Ammo and pursue her around all the map with your own Charge attack, shooting in her face as soon as you make contact with her. That also makes this encounter a spectacular biotic fight. If you're using a shotgun that is effective against barriers (for example, the Geth Plasma Shotgun), you can use Charge to chase her around the battlefield from the start of the fight.
 * If you are a Soldier, you could come into the fight with a fully-loaded Collector Particle Beam, and the evolved skills Inferno Ammo and Improved Cryo Ammo. You can use the Collector Particle Beam to destroy her barrier. For her armor you can switch to your pistol or sniper rifle with Inferno Ammo armed. Finally, when her health bar is exposed, use the Improved Cryo Ammo with any non-heavy weapon and simply keep firing.