An amulet inscribed with the symbol of the Balance and two dragons circling around; it is a replica of the circle on the wall in the Guardian's throne room. The Talisman is mentioned in the Scripture of Reunification. It was held by the Sentinel in the Enclave for the last 10,000 years in anticipation of the 13th Guardian.
Vestrum Tobias gave the Talisman to April Ryan in the mistaken belief that she was the new Guardian. The powerful - but undefined - magic of the Talisman enabled April to jam the Spirit Compass on the White Dragon, in an attempt to divert the ship to Alais. When Captain Nebevay realised what she had done he locked it in a chest in the hold; describing it as bearing "the mark of the Balance and of the Sentinel". April made an attempt to smash the lock with an axe, but failed as the ship was destroyed on the reefs near Tagate. After the White Dragon was sunk, April found her Talisman hanging from a spar underwater after slaying the Snapjaw who had taken up residence in the wreck. As part of her tasks as the Waterstiller, she used it to unlock the niche in the Ancient Shrine to retrieve the Maerum Stone.
In the Guardian's Realm April used her Magic Binding Potion on the Talisman before using it in the Trial of Might against the Chaos Vortex, which caused the Vortex to be absorbed by the Talisman. When April holds up the Talisman to the Vortex, it can clearly be seen that the dragons around the outside of the Talisman are circling as their stone counterparts do in the Tower. They don't appear to move at any other point during the game, so they may be reacting either to the immediate presence of the Vortex, or April's proximity to the Tower.
Having passed the Trial of Might, April carried the Talisman with her to the Guardian's throne room. Gordon Halloway appeared to sense the presence of the Talisman - or his 'soul' the Vortex inside it - and reacted with rage and fear. When he tried to attack April to get it, Adrian defended her, and to stop Gordon she released the Chaos Vortex back to Gordon, making him whole.
The Talisman has not been seen since. Though in Dreamfall concept art April seemed to be wearing a similar amulet (which was black, blue, and red rather than golden in color, like the Talisman in the first game), it vanished in later iterations. It is still possible that she simply wears it under her clothing, as would be unwise to display such an obvious symbol of allegiance to the Sentinel while among the Azadi. Abnaxus, who does not appear in Dreamfall despite Tørnquist's original plans for him, wears a golden amulet in another piece of concept art but the question of whether it is the Talisman remains open.