Assassin

"Masters of the killing arts."

- -Description of Assassins in Fire Emblem: The Sacred Stones.

Assassin is a class that first appeared in Fire Emblem: Rekka no Ken as promoted versions of Thieves. The first Assassin players saw in a battle scene was Jaffar; Jaffar was also the first pre-promoted Assassin that players got to control in a battle. Thieves such as Matthew and Legault could be promoted into an Assassin using a Fell Contract. Assassins returned in Fire Emblem: The Sacred Stones, being an optional promotion for Myrmidons as well as Thieves. In both Fire Emblem: Path of Radiance and Fire Emblem: Radiant Dawn, the Assassin class is exclusive to the character Volke, who fights with knives as opposed to swords.

Combat
It is important to keep in mind that Assassin and the Thief are different classes in regards to combat performance.

The Assassin is considered to be a useful class to have on the field, and if you face one, you'll fear it. When they promote from a Thief, they lose their ability to steal, though they keep their ability to use the Lockpick and to disarm traps. Despite being unable to steal, they gain the potential to be a formidable combat class. On occasion, the Assassin will perform a special lethal attack, in which they will defeat an enemy in a single attack, regardless of HP and Defense. This skill is known as Lethality or Silencer (FE7, FE8). An Assassin's Critical hit has a 50% chance of being a lethal attack. Lethality can even be used on bosses (except final bosses), but with 25% of the Critical hit rate rather than 50%. Also, when an Assassin activates a lethal attack the experience they gain from killing the enemy is roughly double the experience they would have earned if they had killed the enemy through normal methods.

The fragile Thief loses much of its weakness once promoted. Although its defense and health is moderate at best, it's rare for an Assassin to fail to evade an attack (unless they face an overwhelming enemy or tactical disadvantage). Reaching the maximum results in a disappointingly low Strength stat, so it's not unheard of for Assassins to strike for zero damage on heavily armored foes. Be aware of the accurate attacks of Mages, as they'll be able to take advantage of your high Speed, yet moderate Resistance. However, a well-trained Assassin can be an extremely effective killing machine and can take out an entire army with a Killing Edge. The exception to these weaknesses is Volke, who not only has a very high strength cap, but also a high strength growth and base. His defense cap, growth, and base are also much higher than normal assassins, making him a very powerful unit.

Promotions
Being the promoted version of the Thief class (or Myrmidon class in The Sacred Stones and Awakening), the Assassin can not be promoted any further.

In Radiant Dawn, the Assassin is considered to be a 3rd Tier class, exclusive to Volke.

Fire Emblem: Rekka no Ken and Fire Emblem: The Sacred Stones

 * Hp: 60
 * Strength: 20
 * Skill: 30
 * Speed: 30
 * Luck: 30
 * Defense: 20
 * Resistance: 20

Fire Emblem: Path of Radiance

 * HP: 60
 * Strength: 23
 * Magic: 20
 * Skill: 30
 * Speed: 30
 * Luck: 40
 * Defense: 22
 * Resistance: 20

Fire Emblem: Radiant Dawn

 * HP: 55
 * Str: 32
 * Mag: 15
 * Skl: 40
 * Spd: 40
 * Lck: 25
 * Def: 30
 * Res: 25
 * Knife - SS

Fire Emblem: Awakening

 * HP: 80
 * Str: 40
 * Mag: 30
 * Skl: 48
 * Spd: 46
 * Lck: 45
 * Def: 31
 * Res: 30
 * Sword: A, Bow: A

Rekka no Ken

 * Jaffar- The Black Fang's Angel of Death and one of the Four Fangs
 * Jerme- The Black Fang's Death Kite and a former member of the Four Fangs
 * Possible promotion for: Matthew, Legault (via Fell Contract).

The Sacred Stones

 * Possible promotion for: Colm (via Ocean Seal or Master Seal), Joshua and Marisa (for both, via Hero Crest or Master Seal)

Radiant Dawn

 * Volke

Awakening

 * Gecko
 * Jamil
 * Porcus - One of the Deadlords
 * Possible promotion for: Gaius, Lon'qu, and Owain.

Trivia

 * Assassin enemies are exceedingly rare in the Fire Emblem games they appear in. This is most likely due to the Lethality skill being too dangerous for generic enemies to have as it instantly kills a unit based on a luck based chance. For example in the GBA games: there are no Assassins faced in the Arena and the only Assassin boss uses magic swords preventing him from activating his skill.
 * In Awakening, there are more Assassin enemies and bosses. However, outside of DLC and Spotpass, none of them have Lethality equipped on any difficulty.
 * Much like thieves, Assassins are depicted with knives in their Game Boy appearances graphics despite equipping swords.
 * In Awakening, the Assassin and Sniper are tied for the highest Skill cap of all promoted classes. Incidentally, both classes uses bows.
 * The Assassin is also tied with the Swordmaster for the highest Speed cap of all promoted classes. Both classes wield swords and are the possible promotions for the Myrmidon in this game.