I've seen it in some high level psr videos on youtube but don't know what it is.
Blacksmith's ultimate gives him a chance to cast his spells multiple times.
^ That. There is a chance when you cast your stun for example (~275dmg) that it can cast it 4x back to back and you dont have to pay for it! So you deal over a thousand damage instead of 275...
[Guide]The all inclusive guide
From the author of Tip of the Week.
Fact: When you play as BS you never seem to get enough multicasts and when playing against they always seem to get multicasts