The Sentinel specializes in a combination of tech and biotic abilities. Though not as proficient as an adept or an engineer in their respective fields, and lacking some advanced weapon training, the sentinel is considered by most a "jack of all trades, master of none".
If we assume that the standard RPG classes are present in Mass Effect, the immediate correlations would be Soldier/Warrior, Adept/Mage and Engineer/Rogue. As such, the sentinel class can be described as a hybrid between a "glass cannon" mage and a "stealth class" rogue. The description, however, is not be entirely valid for the Sentinel as, although gameplay does focus on disabling enemy defenses with Warp and Overload, and crowd controlling on the field via Cryo Blast and Throw, this class can also soak up a good amount of damage through Tech Armor. The main weakness that plagues the sentinel is the lack of weapons training, being able to use only heavy pistols ,submachine guns and heavy weapons, with the option of adding one extra class of weapons during the middle portion of the game.
For returning players from the first game, there are some major differences that need to be noted regarding powers in general:
- All powers have been greatly simplified either by condensing more of them into one or getting rid of some completely. As such, Sabotage has been folded into Overload, Barrier has become Tech Armor, Lift was reworked into Throw, Stasis has been removed to better facilitate the more action oriented combat, and so on.
- The targeting system has been overhauled dramatically. Most biotic powers travel in the direction of your crosshairs and bend their trajectories when close to the intended target, making it possible to hit foes behind cover.Others ,such as Overload, Incinerate instantly affect your target without having a travel animation.
- All cooldowns have been reduced by a large amount, however, a global cooldown (each power, when used, not only activates a cooldown on themselves but also on all other powers as well,equal to the cooldown of the activated power) has been imposed.
The power uses mass effect fields to hurl targets away, damaging them if they hit an object. It can now be precisely curved around objects and cover to hit its target. Throw really shines when used in combination with pull, in order to reduce the target's mass, launching foes harder against walls or over nearby ledges. There is also an instant kill possibility if the target is frozen beforehand, throwing them at an object can shatter them instantly.Very similar to the soldier's Concussive Shot, although the latter is slightly better by being instant, not having a travel animation, thus missing is a lot harder.
At rank 4 , it can be evolved in two ways:
- Heavy Throw: Adds a significant amount of momentum to the power with which enemies get hit.
- Throw Field: Gives the ability to affect multiple enemies in a small area.
The power spawns a mass effect field that damages enemy targets and stops health regeneration. Warp can be considered the bread and butter of the sentinels' biotic offence, perfectly reflecting the class as a whole, lots of aplications but with limited power. Firstly, as mentioned before, it stops health generation, making it very useful on krogan and vorcha enemies. It is potent against armor, although not as much as Incinerate, and biotic barriers. Lastly, but not least, if the target is affected by another biotic ability, such as Reave, Pull or even Slam with precise timing, it will detonate, causing damage and knocking back nearby enemies next to the target.
At rank 4 it can be evolved in two ways:
- Heavy Warp: The damage of the ability is hugely increased.
- Unstable Warp: Increases the blast radius when Warp detonates biotic effects.
The power generates an energy armor suit that boosts the user's shields. Considering that most enemies will be much more attracted to the commander than his companions, having a powerful, unique defensive power really gives the sentinel an edge on higher difficulties. Once activated, the armor remains in use until destroyed, when exiting a combat zone or reloading. On the odd ocasion that it does get destroyed, it sends out a pulse of energy, knocking back and damaging nearby enemies within a certain radius of the player.
The other defense disabling ability available to the sentinel, Overload focuses on shutting down enemy shields, damaging synthetics and, starting with rank 3, overheating weapons. Again, a very useful multi-purpose ability. Unlike Warp, that deals considerably low damage against shields, overload is very efficient against shields, disabling defenses on no more than 2 or 3 applications.
When activated, the user's omni-tool fires a mass of super-cooled subatomic particles capable of snap-freezing targets within a certain radius. The only crowd control ability available to this class, it also presents the ability to curve over cover, allowing a couple of safe shots to be fired without fear of retaliation. Frozen enemies are also more susceptible to direct damage and can shatter when their health is low enough. However, as any kind of defense will prevent the enemy form being frozen, this ability is definitely sub-par in higher difficulties. Also, frozen enemies tend to fall behind cover, thus negating your opportunity to finish them off. Throw can be used instead to counter enemies charging at you like Krogan, Varren or Husks (once their defenses are down).
As the class ability of the sentinel, it mostly rounds up your statistics by reducing the cooldown time on your abilities, optionally giving them more power, increases your health and gives a negotiation bonus by boosting your Paragon/Renegade points.
As a Sentinel, you'll be constantly spamming all your other powers, so taking a passive power as a bonus is recommended, ammo powers such as Armor Piercing Ammo or Warp Ammo will complement your Sentinel nicely.
After you have enough shield upgrades, you will not have to spam Tech Armor as much freeing up room for Samara's Reave or Tali's Energy Drain. These powers tend to be very redundant on the Sentinel however and you should never max out Reave with Warp or Overload with Energy Drain. In addition, you will also have to consider bringing someone along with Squad Ammo powers since you don't have any yourself. Still they are both very viable options mid to late game.
Finally, you may want to consider Legion's Geth Shield Boost as it compliments the Sentinel's Tech Armor very well.
As your Sentinel is effective against all types of enemies, on lower difficulties you're free to choose the companions of your liking. In hardcore / insane, however, Miranda (Warp, Overload, global health and damage bonus) and Mordin (Incinerate) are a very good choice. With them you can easily disable any kind of defenses. It is highly recommended you bring someone with squad ammo if you don't have an ammo bonus talent yourself.
In missions where you know you'll be facing synthetics, you can swap Mordin for Legion (AI Hacking, Widow Sniper Rifle) or Tali (AI Hacking, Energy Drain).