Promethium longsword

The Promethium longsword is a Tier 10 sword used in the Dungeoneering skill. It can be created at level 94 Smithing with two Promethium bars. It requires level 90 Attack to wield.

It can also be obtained as a drop from Blink, from a level 126 or 138 skeleton wielding a longsword, or from a forgotten warrior visibly wielding the sword or its primal counterpart.

Dropping monsters
Promethium longsword