Fang – Sentinel Crystarium

Character Fang
Role Sentinel
Like Snow, Fang has access to every standard Sentinel Ability (i.e., except Elude), though her lower HP total and relative lack of defensive Weapons makes her a bit less effective than him. She does get Mediguard first, so I guess that's something.
Compare Fang – Sentinel Crystarium to other Crystariums

Related

Fang

Eidolon Bahamut (Chapter 10)
Base HP 390
Maximum HP 24,000
Base Strength 28
Maximum Strength 2,005
Base Magic 22
Maximum Magic 1,300
Starting Weapon Bladed Lance
Primary Roles Commando, Sentinel, Saboteur
Accessory Crystal Saboteur 5
Accessory Crystal Sentinel 8
Accessory Crystal Commando 10
ATB Level Crystal Commando 8
Chapter 7

Fang – Commando Crystarium

Character Fang
Role Commando

Fang – Medic Crystarium

Character Fang
Role Medic
Fang has access to the same Medic Abilities as Lightning, but because it's a secondary Role, she's even less useful as a Medic. By the time you are likely to learn these Abilities, the lack of a Curasa spell means Fang will be terrible at healing. Her only real advantage over any other Medic is that she gets Raise (which Sazh and Snow do not), but you're more likely to use Renew or a Phoenix Down late in the game anyway.

Fang – Ravager Crystarium

Character Fang
Role Ravager
For a secondary Role, Fang is a damn effective Ravager. (This seems even stranger since she's the only Character who doesn't have Ravager as a primary Role.) She has access to every spell through tier 2, and while she only has two -ga spells, one of them is Aeroga! Perhaps her biggest disadvantage as a Ravager is that her strength is so high that she's more effective in other Roles. However, she does gain all four -strike Abilities, so even this isn't really a problem.

Fang – Saboteur Crystarium

Character Fang
Role Saboteur
Though she lacks Vanille's Death Ability, Fang is perhaps the most effective Saboteur in the game, though her one glaring weakness, an inability to inflict Poison, is a problem against many of the toughest foes in the game. She also lacks the defense-lowering multi-target debuffs (Deprotega, Deshellga, Imperilga), but as a general rule you're only attacking one target at a time anyway, so this is not a big deal.

Fang – Synergist Crystarium

Character Fang
Role Synergist
Fang is an interesting Synergist that can be quite effective despite having less Abilities than any other Character. She has access to Veil and Haste, but more importantly she gets the high-powered Abilities Bravera, Faithra, Protectra, and Shellra. These Abilities, exclusive to Fang and Vanille, are more powerful versions of the Abilities they are based on, but have a much shorter duration. You'll have to pay a lot more attention to your buffs if you use them, but the payoff can certainly be worth it.

Hope – Sentinel Crystarium

Character Hope
Role Sentinel
Despite having the lowest HP in the game, Hope makes for a fairly interesting Sentinel. Like Lightning, he doesn't get Challenge and favors Elude over Mediguard and Steelguard, but Hope also gets the counterattack Abilities, Entrench and Vendetta. He's fun to play around with, but not much use against truly powerful enemies.

Lightning – Sentinel Crystarium

Character Lightning
Role Sentinel
Lightning is an interesting Sentinel, relying on the Elude Ability rather than Mediguard or Steelguard. This Ability (the only one she can use besides Provoke) allows her to dodge attacks with a very high rate of success. However, it only works on Physical attacks, making Lightning a sitting duck against Magic-wielding foes. Still, when it works, it's very effective and requires very little healing.

Sazh – Sentinel Crystarium

Character Sazh
Role Sentinel
Sazh is all about defense as a Sentinel. That may seem to go without saying, but he doesn't get any evasion Abilities, and while he does get Vendetta he does not get Entrench or the Counter auto Ability. He also doesn't get Mediguard, so if Sazh is your defender, you'll need to keep an eye on his HP. He does have the second-highest HP total in the game, though, and is the only non-primary Sentinel with Challenge.

Snow – Sentinel Crystarium

Character Snow
Role Sentinel
Snow is the prototypical Sentinel, gaining every Ability except Elude. Snow's job is to stand there and take punishment. While he has the same Ability list as Fang, Snow is a bit better as a Sentinel because of his high HP total and access to Weapons with the Improved Guard and Improved Ward abilities.

Vanille – Sentinel Crystarium

Character Vanille
Role Sentinel
Vanille as a Sentinel? Surely not! And truth be told, she's not very good at it. She has Mediguard at least, but not much else, including Challenge. She does have more HP than Lightning or Hope, but both of them are evasion Sentinels anyway. Basically, you don't want Vanille to be your main Sentinel. She's fine in the Tortoise (SEN/SEN/SEN) paradigm, but not much else.

Sentinel

Bonus Type Damage Reduction

Sentinel

Abbreviation SEN
Role Bonus Damage Reduction
Base Bonus (Self) Damage Resistance: +40%, Wound Resistance: +30%
Role Level I Bonus (Self) Damage Resistance: +45%, Wound Resistance: +33%
Role Level II Bonus (Self) Damage Resistance: +50%, Wound Resistance: +36%
Base Bonus (Allies) Damage Resistance: +7%, Wound Resistance: +5%
Role Level II Bonus (Allies) Damage Resistance: +9%, Wound Resistance: +7%
Role Accessory Defender's Topaz (Grants Damage Resistance: +3%, Wound Resistance: +3% to self)