HYDRA

HYDRA is a fictional terrorist organization in the Marvel Universe. The organization first appeared in Strange Tales #135. In its original continuity, it was headed by nondescript businessman Arnold Brown, who was killed as S.H.I.E.L.D. apparently crushed the organization. It soon returned, however, headed by Baron Wolfgang von Strucker, with the support of the Nazi Red Skull; HYDRA's changing origin was one of the earliest Marvel retcons. After its initial defeat, several of its branches surfaced, appearing to be unrelated and independent. HYDRA's scientific branch was initially A.I.M. (Advanced Idea Mechanics), which later split off into its own organization. Other factions included THEM and the Secret Empire.

Despite the name's capitalisation per Marvel's official spelling, the name is not an acronym but rather a reference to the mythical Lernaean Hydra. The organization's motto references the myth of the Hydra, proclaiming that if a head is cut off, two more will take its place, proclaiming their resilience and growing strength in the face of resistance. HYDRA agents often wear distinctive green garb featuring a serpent motif.