Spectres are agents from the Office of Special Tactics and Reconnaissance and
answer only to the Citadel Council. They are elite military operatives,
granted the authority to deal with threats to peace and stability in whatever
way they deem necessary.

They operate independently or in groups of two or three. Some are empathetic
peacekeepers, resolving disputes through diplomacy. Others are cold-blooded
assassins, ruthlessly dispatching problem individuals. All get the job done,
one way or another, often operating outside of the bounds of galactic law.

The Spectres were founded after the salarians joined the Council. For many
years, they operated in secrecy, as back-room 'problem solvers.' Only after
the krogan Rebellions did their activities become publicized. Assignment of a
Spectre is less contentious than military deployment, but makes it clear that
the Council is concerned about a situation.