Lands of Algia 4E
Glistening with electric-blue eldritch energy, this weapon's blade packs a stormy punch.
Enhancement: +1 attack rolls and damage rolls
Critical: +1d6 thunder and lightning damage per plus
Power (Daily * Lightning): Free Action. Trigger: You hit an enemy with a lightning power or a thunder power using this weapon. Effect: That enemy is knocked prone. It’s also deafened and takes ongoing 5 lightning damage (save ends both). Published in Adventurer’s Vault 2, page(s) 23.
Found in the main chamber of the Temple of Nerilous