This is called the Tome of Balanced War Axe.
Under combat skills (alt c) it's called Balanced War Axe.
This tome can be aquired from the main floor of the library in POK and in Ship City outside of Nedaria's Landing and other various locations I'm unaware of.
Give it(and all tomes and disciplines) to your GM (use the find button to find GM's and Tome Merchants) to learn the skill.
When used consumes one "Basis Axe Components" and produces a stack of 20 Balanced War Axe used for throwing.
Balanced War Axe stats are:
MAGIC ITEM NO DROP
Slot: RANGE
Skill: Throwing Atk Kelay: 29
DMG: 17
WT: 1.0 Range: 150 Size: LARGE
Class: BER
Race: ALL
Hope this helps all my fellow Berzerkers out there.
Ohrson
Avenging Storm
Seventh Hammer