Up to 5-20% Strength based on the charge time of your heavy attacks. Stacks 3 times.
3.5-5% Strength for 3.5s on Hit. Stacks 5 times.
6-12% Critical Chance for each Enemy Hit by your previous attack. Stacks 5 times.
Increased Cleave on Critical Hit and gain 10-25% Ranged Attack Stagger.
Best pared with Ogrynn heavy hitter aura. Every damage buff does matter in this build.
As of patch 15, headtaker doesn't proc with flames. But i think cleave still transfers to melee oddly enough.