The Sniper is the promoted version of the Archer, and a foe to be feared, especially if you're keen on air units. While not particularly different from normal Archers, the Sniper is open to the higher class bow type weapons. While they do recieve a significant boost in defense and health, they're still very vulnerable targets and can't take very much punishment. Archer and Sniper classes will often dodge many attacks directed at them, but it's risky to rely on those abilities. Like Archers, Snipers can also use Ballista.
Snipers fight exactly like their Archer counterparts, only with more power. See Archer for more information. Like Myrmidons becoming Swordmasters, Archers becoming Snipers receive much higher critical hit chances.