Zombie Generals

Structural lore — what Oda has confirmed about this. Mysteries (unsolved questions) live in Vault/Threads/; this is what the world IS.

What we know

Ch. 452: An elite tier of Thriller Bark zombie, “completely different from the other zombies.” Each was a powerful warrior in life — examples cited: “the head knight of a country, a fierce criminal, a legendary samurai, a pistol master” (pp. 9-12).
Ch. 452: Reanimated by Gecko Moria’s shadow-theft and “made immortal” — they feel no pain and do not tire (pp. 9-12).
Ch. 452: They wear armor and wield real weapons; ordinary attacks are largely ineffective (“all those attacks were ineffective against one of them,” p. 12).
Ch. 452: Each general carries a stolen shadow, inheriting the donor’s abilities and personality — e.g. Jigoro of the Wind fights with Zoro’s sword style and recites his creed (pp. 13-14). See Thriller Bark Zombies Carry Their Owners Shadow Abilities And Personality.
Ch. 452: Flagged weakness — they can “malfunction” when struck by “true fear” / confronted by “real zombies” (pp. 9-10).

Named generals shown so far:

Jigoro of the Wind — carries Zoro’s shadow (One-Sword Style swordsman who “perished at 59”).
Taralan — “Spider Monkey” chimera general; hauls Luffy’s coffin.