Faceless Men

The Faceless Men are an organisation based in the Free City of Braavos, though their members range far and wide across both Essos and Westeros. They are reportedly a guild of assassins who command extortionate fees, but have a reputation for competence that is unmatched by any comparable organisation.

In the books
In the Song of Ice and Fire novels, the Faceless Men are based at the House of Black and White, a temple in Braavos dedicated to the 'Many-Faced God' that everyone will face (a reference to death). Whilst they are indeed a guild of assassins, they have philosophical and religious motivations that will lead them to rejecting commissions that clash with those motivations.

The Faceless Men are a fairly old organisation, predating the Doom of Valyria. Their ancestors worked in the mines under the Fourteen Fires, the great volcanic mountain chain whose eruption destroyed the Valyrian Freehold four centuries ago.