The Avatar's Ankh seems to be unique, and is a relic of old adventures. It does not seem to have any use in the game, though it is a symbol of life as well as of virtue.
The Snake Amulet is Lord British's talisman with a lengthy history behind it. It was used to summon Lord British to Sosaria in the dark times of Akalabeth, and was used by Lord British to summon the Stranger through a blue moongate called Siege Perilous the first time. It was used in the time of the Shadowlords as a way past the darkness surrounding Dungeon Doom. It has no apparent use in Ultima VI.
The Amulet of Submission cannot be removed once worn. Lord Draxinusom gives it to the Avatar once he surrenders, and it is essential because the Avatar has all the Gargoyles' respect and cooperation, as well as assistan
