What is Hades' emblem?

Answer 1

There are many to chose from, his possessions ranged from the immortal horses of his golden chariot which he used to kidnap Persephone, the Helm of Darkness which was a helmet that made the wearer invisible, the staff of a three-forked scepter which opened the way into the realm of the dead, the Palace of Hades where he dwelt in the Underworld, as well as the Throne of Hades where he rested therein, the Keys of Hades that the Judge of the Dead Aiacos keeps, Cerberus himself is sometimes a symbol of the Underworld as he is the guardian of the gates -or house - of Hades; the orchard or Hades from where Persephone ate pomegranate seeds; the cattle that Hades kept.

His bird was the screech-owl, his trees were the white poplar and cypress, his plants the mint and asphodel.
There are many to chose from, his possessions ranged from the immortal horses of his golden chariot which he used to kidnap Persephone, the Helm of Darkness which was a helmet that made the wearer invisible, the staff of a three-forked scepter which opened the way into the realm of the dead, the Palace of Hades where he dwelt in the Underworld, as well as the Throne of Hades where he rested therein, the Keys of Hades that the Judge of the Dead Aiacos keeps, Cerberus himself is sometimes a symbol of the Underworld as he is the guardian of the gates -or house - of Hades; the orchard or Hades from where Persephone ate pomegranate seeds; the cattle that Hades kept.

His bird was the screech-owl, his trees were the white poplar and cypress, his plants the mint and asphodel.

Answer 2

his invisibility helmet, also known as the Healm of Darkness