What is Rune Master for? (Diablo 2)

The Runemaster is a clear ax with 3-5 sockets that you can insert into:
SpoilerShael-Sol-Shael-Shael-Shael (+9 Min Dmg; 80% Incresed Attack Speed)
Sur-Shael-Shael-Shael-El (80% Increased Attack Speed; Hit Blind Target; +1 To Light Radius)
Ral-Ral-Ral (15-90 Fire Dmg)
Ral-Ral-Ral-Ral-Shael (20% Increased Attack Speed; + 20-120 Fire Dmg)

But if you download , for example Stun skill, you can use BA of Firebolts * + Rune Master, as an option BA * + Barbed Shield Shield (SurEl (50Mana / + 15def / 1LightRadius)



* which CtC on attack *.