The Specter is a monster featured in Silent Hill: Requiem. They are one of the very few monsters currently known that are able to use firearms, and most likely the only ones able to use them effectively in combat.
The Specters resemble US Marines, in their form and clothing, often wearing kevlar vests and sometimes helmets. They will mostly utilize Glock 17s as firearms, but as they grow more advanced, some can be seen weilding M4A1 assault rifles. These weapons however are technically not real, as they quickly disappear when the Specter is defeated, not allowing Logan to pick up the weapons. The Specters will act like actual military men, effectively using cover and firing accurately and communicating with their team mates. Due to this, Logan is forced to only engage them at long ranges to avoid certain death, and he must use his training and experience to the fullest to defeat large groups at a time. Logan has a distinct advantage against Specters at short range, due to his fluency in close quarters combat, allowing him to take out these enemies in hand-to-hand and melee combat.
The Specter symbolises Logan's fellow Marines, more specifically the ones who fell in battle right at his feet. They represent his guilt at not being able to save them, and his regret in that he may have been able to do things differently.