Zaishen Medallion

Zaishen Medallions could be found during the Guild Wars Nightfall PvP Preview Event. You could exchange them at the Zaishen Supply Masters for one of the following items:
 * Flame of Balthazar
 * Crème Brûlée
 * Flask of Firewater
 * Celestial Sigil

Acquisition
The Zaishen Medallion could be found:
 * Core
 * Battle Isles
 * Random Arena
 * Team Arena
 * Heroes' Ascent
 * Guild versus Guild